The remnants of a Fedback FG600 England made function generator of 1975. Someone clipped the legs of one of those canned devices of the time leaving
10 longish pins in the board. Overlay is a circle with a tab. He wrote RC4195 and RC4185 on pcb. Now a Raytheon RC4195 looks right there, a dual tracking +/-15V regulator but what was an RC4185 I cannot find any reference to it , but it may have been the original device and he intended replacing with a 4195. The drilling pattern was 8 like standard DIL and one between 1 and 8 and one between 4 and 5 but of course may have been bent to that form , from a circular TO96 type package.
7815 + 7915 will go in there firstly for proving purposes in all likelihood
Here's a theory, maybe the lettering was abraded but he wanted to memorialize what info he had right on the board before he headed to the reference library or the parts store with the IC in hand.
Interesting you say that Another IC he'd marked on the board , but still in place is a Plessey multi transistor pack It is that chalky print of the time and wrote SL304?? 5C? With good slant lighting , perhaps decades on I could confirm SL3045C
But RC4195NB is not a 10 pin pack if the 5th character was indistinct
Take it to a forensic print analyst. They can analyze under polarized and oblique lighting of various wave lengths through various filters your sample and tell you what was written.
Is it a genuine outfit ? ie does a "Request for Quote (RFQ)" return mean they actually have one assuming you cough up 300 USD .
Although footprint is 10 pins , only 9 have traces to them, but wire size legs rather than the TO66 package pins and overlay would suggest TO66. I wonder if the 4185 was not-fixed +/-V. My old Raytheon book seems to suggest they used TK suffix for TO99 and TO66
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