Caseback.

[fjseal]

This snap-off caseback does not seem to have either a tab or a groove for the case knife after a careful search. It came off with a thin-bladed knife no problem. Is this unusual?

[KarlvonKoln]

If I'm wrong, I will happily swallow my pride and say no more...but I would bet all the money in my pocket that this watch is a front-loader.  The case back is so much smaller than most, such that trying to remove the movement through there would seem too unusual.  And the way there's a bump over the stem entrance; I see that a lot with front-loaders. 

I know it has steel mated to gold, but I have a front-loader that is like that myself.  It fools you.  If it is a front-loader, you will need a crystal lift to remove the crystal, or if there is a tension bezel on top, that will need to come off.  It is likely to have a two-piece stem, so you will need to *gently* pull out/off the crown end of the stem - it will snap free.  The movement *should* lift right out.  (Unless it is one of certain models of Omega, in which case you will need to unlock it.)

I can better advise you if you could post pictures of the front, and crown-side edge, and opposite side edge, so I can see the make, model, style, and whatever else there is to go on.  I still could be wrong, but I feel we are looking at a front-loader. 

[HectorLooi]

Let's have a look at the front too. Some of these front loaders need the crystal to be "blown" off with air pressure. I think mark has a video on YT showing how it's done. 

Found it.

[fjseal]

Thank you for your replies, but I only posted the pic out of curiosity. I managed to prise the back off and changed the battery so it is functioning well now, thanks. PS-why would you not have a lip or groove to insert case knife?

Edited July 4, 2023 by fjseal
Final thought.

[Galilea]

On 7/3/2023 at 7:41 PM, KarlvonKoln said:

If I'm wrong, I will happily swallow my pride and say no more...but I would bet all the money in my pocket that this watch is a front-loader.  The case back is so much smaller than most, such that trying to remove the movement through there would seem too unusual.  And the way there's a bump over the stem entrance; I see that a lot with front-loader,

I am so glad you mentioned that because one of my beginner burning questions is about that. I should look at my watches to find out which, but it is either Helbros or Benrus that has this as a standard, and I never know what to do with these. It says right on the back "Open through front/crystal", something like that.  

They might deal with that in the courses here (which I signed up for and anticipate starting this week) but in the meanwhile i am super curious about this. I notice you advised the OP to send pics, which I can do if needed,  but if there is a standard way for the brands I mentioned, I'd like to know. Thank you.

[KarlvonKoln]

5 hours ago, Galilea said:

"...Helbros or Benrus ...  but if there is a standard way for the brands I mentioned, I'd like to know. Thank you."

I have a couple Helbros and a couple Benrus, all of which have ordinary removeable backs.  I'm afraid I know of no standard.  Sometimes, a watch manufacturer will make models that are front loaders.  And of those models, sometimes they will have a front bezel which must also be removed, and sometimes not.  Over time, you learn what to look for.
And EVEN STILL (as was the case above) you can still be wrong.  Some watches just make it hard for us at times.  When it comes to opening watch cases, the best advice I ever received was "Proceed with caution".

[Geotex]

The Benrus "Open Thru Crystal" waterproof cases were meant to be opened with a crystal wrench, which is a flat tool with a cutout circular head that is matched to the crystal size and can very quickly and easily take off the crystal.  However, unless you have an interest in collecting those tools, they also come off easily with an adjustable multi-prong crystal lift, which is a tool more readily available new or used at a range of price points. These also have two-piece stems, so the crown is carefully pulled off to release the movement out the front.

But if you are interested in the original Benrus-branded tools, they can be found in the used marketplace. They are matched to the crystal diameter, so it isn't a one-size-fits-all situation. However, there are multiple case numbers that can share each tool, even though not all are listed on any one wrench. Here are some commonly-seen equivalents that I think are correct, including the 2nd tier Belforte line case series numbers:

3021/3031/9021 

3001/3011/3041/3051/3061/7001/9045/9061/9064/9081

3056/9056

There are also some with a plastic insert that allowed them to be used with square or oval crystals, such as 3142 and 7110.

[Galilea]

4 hours ago, Geotex said:

The Benrus "Open Thru Crystal" waterproof cases were meant to be opened with a crystal wrench, which is a flat tool with a cutout circular head that is matched to the crystal size and can very quickly and easily take off the crystal.  However, unless you have an interest in collecting those tools, they also come off easily with an adjustable multi-prong crystal lift, which is a tool more readily available new or used at a range of price points. These also have two-piece stems, so the crown is carefully pulled off to release the movement out the front.

But if you are interested in the original Benrus-branded tools, they can be found in the used marketplace. They are matched to the crystal diameter, so it isn't a one-size-fits-all situation. However, there are multiple case numbers that can share each tool, even though not all are listed on any one wrench. Here are some commonly-seen equivalents that I think are correct, including the 2nd tier Belforte line case series numbers:

3021/3031/9021 

3001/3011/3041/3051/3061/7001/9045/9061/9064/9081

3056/9056

There are also some with a plastic insert that allowed them to be used with square or oval crystals, such as 3142 and 7110.

Very helpul! I may already have one or some of these tools but not have known what it was. Off in search of images. I did think the stem removal was a two part process, but was stumped beyond that and never made the connection between the watches, that this is for the waterproof ones. Thanks.

[Neverenoughwatches]

6 hours ago, Geotex said:

The Benrus "Open Thru Crystal" waterproof cases were meant to be opened with a crystal wrench, which is a flat tool with a cutout circular head that is matched to the crystal size and can very quickly and easily take off the crystal.  However, unless you have an interest in collecting those tools, they also come off easily with an adjustable multi-prong crystal lift,

I have something from robur that works in a similar way to individual wrenches. It works really well. The other is a bergeon crystal lift for future reference for galilea and fjseal.

[Galilea]

Check. I just got a vintage Vigor lifter kit on ebay, I think for a decent price. It did not come up under the usual search terms, and was stuck in the wrong category, so I Bought it Now.

I believe I have a tool similar to the first one neverenoughwatches shows above.

I do for fact have a very large box/small cabinet of a tool that puts them back on, and it came stuffed full of replacement crystals in every size, up through 18s and some specialty sizes. It is billed as a revolutionary new thing and all the crystals are plastic. It's just a shame that they have all yellowed considerably, even brand new, in their unopened packets, in the dark of the box, in the back of a closet, in the corner of my lair.  I would have thought they needed air or light exposure to do that.  If I can get pics taken I will edit this post and add them.

Edited July 8, 2023 by Galilea
had vevor, when it is vigor

[Geotex]

It's a fun rabbit hole to explore - many options have popped up over the years.  One thing I find interesting is the different ways toolmakers provided us with a means to load up a crystal for installation – it's important to get just the right depth of grip. The two terraced rings that are part of the Electro-Vice set (see below) tend to work better for me than the sliding tray shown above, but it isn't obvious that they go along with the crystal lift tool so you often see them being sold alone in watchmaker tool lots. 

[Neverenoughwatches]

10 hours ago, Galilea said:

Check. I just got a vintage Vigor lifter kit on ebay, I think for a decent price. It did not come up under the usual search terms, and was stuck in the wrong category, so I Bought it Now.

I believe I have a tool similar to the first one neverenoughwatches shows above.

I do for fact have a very large box/small cabinet of a tool that puts them back on, and it came stuffed full of replacement crystals in every size, up through 18s and some specialty sizes. It is billed as a revolutionary new thing and all the crystals are plastic. It's just a shame that they have all yellowed considerably, even brand new, in their unopened packets, in the dark of the box, in the back of a closet, in the corner of my lair.  I would have thought they needed air or light exposure to do that.  If I can get pics taken I will edit this post and add them.

Yep do that, pictures please matey. 

8 hours ago, Geotex said:

It's a fun rabbit hole to explore - many options have popped up over the years.  One thing I find interesting is the different ways toolmakers provided us with a means to load up a crystal for installation – it's important to get just the right depth of grip. The two terraced rings that are part of the Electro-Vice set (see below) tend to work better for me than the sliding tray shown above, but it isn't obvious that they go along with the crystal lift tool so you often see them being sold alone in watchmaker tool lots. 

Nice selection, If you cant get a crystal off Geotex then no-one can.