Selecting the right crystal for project #2

[ColinC]

Here is project #2.

I scrounged this watch from my Aunt and apart from the cracked crystal it appears in excellent condition and runs well

I don't own a timegrapher yet but If I rest the watch over the letter Q on my laptop and use tg-timer it says it is running about +14s a day

I have searched online stores and found similar watches from the same producer in the $30 - $50 price area - but then I also found this
https://kibblewatches.co.uk/products/1960s-lusina-geneve-manually-wound-linen-dial-on-strap .  I know it isn't exactly the same as the movement doesn't look like a ETA 2391

Not sure if I am ready for this watch but I have already popped the crystal out, measured it and put it back in again using a fairly cheap press that says for mineral glass...  

When I go to order a crystal (or 3) I am swamped with options!

I have looked at cousinsuk and there are different brands, different dome heights steps and no steps etc.

Using a set of digital calipers I measured the diameter of the old crystal to be 30.20mm (3 readings between 30.23 and 30.28). I also measured the height to be approx 3.50mm

Am I right in thinking I should not buy the low domed crystal (N Sternkreuz) which according to the spec sheet has a glass thickness of 1.2mm and an internal height of 1.9mm because the sum of these 2 is less than the 3.5mm I measured?

The high domed without step (Sternkreuz Hw) doesn't specify a glass thickness but has an internal height of 2.7mm - I don't think I want this as the one of the features I like most about this watch is how thin it is....

Then there is a high domed with step (Sternkreuz Hws) which looks to be even taller with an internal height of 3.0 and glass thickness of 1.4

There is a domed slightly (Sternkreuz M) which appears to be less flat across the top than the others (at least in the profile pic) and much less like the original crystal, where the watch hardly rocks at all when placed face down on a flat surface.

Also is it possible to upgrade this watch by putting in a mineral crystal? 

[LittleWatchShop]

Based on my experience, as an amateur, you are gonna have to buy several candidate crystals and pick the one that works.

[Charette]

I believe (and don't quote me 100% on this) that this type of bezel will not accommodate a mineral crystal, as to install you need to flex the crystal in order to reduce its diameter and fit it in the watch. Once your press is off it will expand slightly again and be held in place under the lip.

You cannot bend a mineral crystal. 

Sticking with an acrylic crystal will keep the charm of the watch, and they are easily polished also if you get some small scratches.

Your logic sounds reasonable to rule out the low dome, but with only a 0.4mm difference it may still work OK for you, if that is your option for a 'regular' crystal. It is nice you have those specs - my vendor in Canada just shows photos of the crystal profile, no measurements.

You should fairly easily be able to tell if your crystal is stepped or not.

Good luck! As LittleWatchShop noted, there may be some purchases here and there that are learning experiences.

[Klassiker]

I would try the Sternkreuz N first, and only go for something higher if it does indeed press on the hands.