I have not been able to find a verifiable reference (yet) as to the case material for the Sprague axial wet capacitors (M39003/01) CLR25. The fifth line is the date code 8337c (1983 - 37 week), so these are 32 years old. In your pictures, I can see a few date codes on other devices, like the TO3 transistor has a date code of 8348, so board was made 1983 or early 84. I do know they are no longer in production. Military/NASA no longer maintains spec library on these either, stopped using these type 1992/93.
With only a educated guess, I would say they are probably silver cased, as all early wet tantalum capacitors used silver cases. A M39006/01 is the first wet capacitor specs for wet TC's. I'll keep looking for info, as I want to know. Do you have silver/gold test acids? That would be a 100% way to verify silver case!
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