Below is a closer one that shows the calibre numbers. I took it years ago to show the visual differences between the 1510, 1511, and 1516.
Kurt, I do not think you will find a photo without the gray plastic. I think the gray plastic is a part of the electronic module that cannot be removed. I have an old parts list from the cal 1510 -- very similar to the 1516 -- and it has a drawing of the module with the gray plastic piece that is labeled with part number "1510.9150 Electronic Module."
As of several years ago, STS in the UK still worked on these watches. If you Google "HEQ forum" (high-end quartz), you will find another watch forum that specializes in these sorts of things. You may want to ask there for guidance, since many people on that forum are enthusiastic about these wonderful watches!
