That's tough if you try to recover the function of the card from that lousy image. I guess you don't have access to the hardware yet, so you won't be able to provide a better picture. Some things can be recovered from that image, though:

• The big Intel chip at A/B 63-83 is likely a micro-controller. The pinout is plausible for a 8051-type processor, and the type number might actually be P8051. It looks like the digit at the spot where the 1 would be is less wide than other digits.
• The 74LS373, an 8-bit latch, is connected to "Port 0" of the 8051. This makes me confident that it is a 8051, not an 8048-series processor.
• The metallic chip at E 80 is the clock generator for the processor.
• The ROM chip at A/B 46-58 contains data for the 8051.
• The 32KB RAM chip at E44-E58 has its 15 address lines connected to two pairs of address drivers: The pair of 74LS244 in row C drives 8051 controlled addresses, whereas the pair of 74LS244 in row F drives ISA addresses. The obvious conclusion: This chip provides 32KB shared memory. The fact that the input of the row-C drivers seems connected to the ROM address lines supports the idea that the ROM is on the 8051 bus, not the ISA bus.

Too bad the chips further to the right, especially in columns with number below 33, are so dusty and/or out of focus that you can't make out any model numbers.

There is no conclusive evidence that the RCA-type jack is actually used for composite video - it might be anything. The card does not seem to be a video card, as it neither has an integrated CRTC or enough TTL chips to generate video timings. The 8051 is too expensive to substitute an CRTC like the 6845. So I guess the card interfaces some custom hardware.

^Great analysis IMHO 😎
I second, it's likely a special purpose board.
An RCA/Cinch/Phono plug could interface with about anything, not just composite.
Might be a signal generator, a form of digital multimeter etc. It could be anything, I'm afraid. 😅

Maybe the data in the EPROM chip contains a copyright string?
If so, this would provide further hints. 🙂

Yeah, I unfortunately don't have the hardware at hand yet and the seller wasn't too interested in cleaning things up and sending me clearer photos. Thanks for the analysis and assessment, this is interesting!