Hi IkeFox, that's an interesting card - thanks for sharing!

I'm also curious. Must be video related,but I don't know what it is.

Maybe some sort of title generator?

The card is from the late 80/early 90s, likely.

Because, if it has older, the card design would be more 80s-like (like original AdLib).
And if it was never, the logic chips would be in SMD form.

Also, these RGB-Compsite converters became very rare in the 90s.

The French NES had one, too, which converted PAL signals to RGB.
That way, the French user could use a SCART cable.
Because, French Color TVs of the 70s/80s didn't support PAL. Just SECAM and RGB.
And SECAM was very difficult to generate, so early computers/consoles avoided it whenever possible.

It looks like it simply is a RGB to PAL composhit encoder that doesn't do anything else in the PC than use its power. You can see how none of the address and data pins are connected.