Hi Slinfiniti
We would need more details to determine which crystal(s) you may need. Just the pictures of the watches do not convey the needed info. For these two older watches, there is not a "case number" which corresponds to crystal replacement size.
For the green gold Bulova, the case number conveys information which was probably used by Bulova internally for accounting/production purposes and perhaps other info we don't understand yet. Between apx 1925-1949 the first digit of the case serial number corresponds to the year in which the case was manufactured- by decade. So a watch from somewhere in the 1920's with a first digit of case SN beginning with a 7 would indicate the case was manufactured in 1927 etc... It is also a unique identifier for said case.
The movement serial number is also a unique ID for said movement, probably also used internally by Bulova for manufacturing accounting. These two SN's don't give info which would be useful in getting a crystal.
What is needed is precise measurements for the length and width of the opening of the bezel in which the crystal fits. There are also various "shapes" of crystals for different watches along with the above measurements.
You would have to measure the width at the horizontal bezel openings in two locations. 1. The narrowest (at the top and bottom). Should be the same on both top and bottom. 2. The width at the widest point in the horizontal plane.
Then measure the vertical "height" of the opening. These three measurements, along with the shape and concavity/convexity of the watch would give us a general idea for size and shape of replacement.
With just the pictures, it's like taking a photo of your 1976 Toyota Tercell into a locksmith and asking him to make a key for the car.
We have several crystal catalogs on site. Try downloading or looking at a few and you'll get familiar with different terms for shape and sizes available. This is something that your jeweler should easily be able to do. They would be very familiar with the process. They should also be able to source a replacement for you. ....or if you supply those measurements and shape to members on site, they may have a replacement for you. Do a YouTube search for "how to replace a wristwatch crystal" and you'll find several videos outlining the process so you can do it yourself.
I am having the old Bulova crystal sent back to me, I would be happy to send it to the appropriate source. Who would like to volunteer.
The Elgin measures 22.40 x 22.40 or as nearest as I can measure. What I do not know about the Elgin is the height profile of the crystal
I have some addtional information to hehlp me with my quest to find my Bulova watch crystal. I have the following makers number that seemed to work. It was a Federal crystal Number T11-230-174
I hope this helps. I was able to obtain the Elgin crystal that I was looking for