Hamilton Khaki GMT repair help

[Pdx]

I just found a slightly older Hamilton GMT and it needs a bit of help.  It is one of the models with two inner rotating bezels.  The crown for one of the bezels comes right off.  Before I take the movement out and remove the second internal bezel gear to see how it works,  are there any blueprints I order for me to figure out what parts I need?  The internal gear still works, but the key that attaches to the crown is missing.  I’m not sure I want to spend $80 for the service center to replace a $10 part.  

[Chopin]

Can you provide better pics ? Has the stem connecting the crown to the movement snapped ?

[WatchMaker]

The basis of your watch is an ETA 2893-1 or -2 which Hamilton adds extra features to (the rotating bezels you mention) via two supplementary crowns. The technical sheet for the 2893 can be found here ... https://www.cousinsuk.com/PDF/categories/15_ETA2893-1,2,3.pdf ... but this won't include the Hamilton additions. 

A normal watch has a single crown and that screws onto a threaded stem and it is the stem which interfaces with what are called the 'keyless works' to allow different setting positions for changing the time, quicksetting the date etc.

However we're dealing with a Hamilton supplementary crown in your case and what looks a little odd is that your crown seems to have nothing to screw onto a stem. It is usually the stem itself which is the weak spot and some remnant of where it screws onto the crown would be apparent; your crown looks hollow (and there is no remaining stem in the watch itself by the looks of it either). But this is a Hamilton special part and because I assume it simply rotates a reference bezel then it is not a normal crown/stem situation and Hamilton provide a special all-in-one-part (my guess).

And herein lies the rub ... how easy is it to get hold of one of these? I suspect it's not going to be the $10 you assume! Even if you're confident about working on a mechanical watch  I wouldn't go fiddling inside until you're sure you can get the part!

[Pdx]

So, the spring with the small metal piece in it apparently sits on top of the gear and it is housed in a sliding tube.  The crown has a gasket that holds the tube through friction.  It would appear that all the parts are there, but I may need to replace the gasket in the crown.  

[WatchMaker]

Hopefully someone more specifically experienced with the Hamilton GMT can assist but just my input... 

A gasket (o ring) is normally only for sealing i.e. to make a screw down crown waterproof. A small spring is incorporated in such a crown so on unscrewing it naturally pushes away from the case for use. It would be an odd design to have a crown that with spring can be removed. If I'm understanding you correctly and it is the tube that interfaces with the bezel isn't it more likely that the tube was affixed to the crown originally? Can you check the second supplementary crown situation, which presumably has the same design, and see? It could be that the fix is to superglue the tube back to the crown so they form the all-in-one-part originally surmised. 

[Pdx]

I was planning on taking the second crown off to see how the whole thing works, though I pulled a bad gasket out of the crown from above.  I was able to get the crown to work properly, though only intermittently.   I believe that the gasket is meant to hold the crown to the tube and the spring pushes out the crown when unscrewed.  When the sliding tube rotates, it rotates the gear for the internal bezel.  I’m planning on sending the watch in to Hamilton as it is $50 to replace all the gaskets  and pressure test it.  I bought the watch planning on selling it, and since I got a really good deal, I feel that it will sell better with a Hamilton service center re-gasket receipt.