nfg.forums

I have a bunch of uncovered (bare pcbs) Sega cartridges.  They don't fit to MS nor MD. There's three different types:
1) a board that says 171-5081 and has one chip on it (MPR-5550 or MPR-5431)
2) a board with 171-5044 printed on it with also one chip (MPR-5553 or MPR-5550)
3) a larger board that reads 171-5067, and has year 1983 printed on it. It has chip labeled MPR-5512 plus seven other chips. They're 4 x Nec (8415KY905), 2 x Mitsubishi (M74LS157P) and one TI (SN74LS32N).

Does anyone have any clue about these? I don't.

You're giving the least helpful information.  How many pins on the connector?  What's the size?  Got a picture?

Right. 22 pins on both sides, almost 2 mm wide each, as well as the gaps between them. The small boards are about 7 cm x 7 cm, while the bigger one is 7 cm x 9 cm. The boards have two holes in them at the sides, diameter 6 mm, about 5 cm away from the connector edge. The traces seems to be gold. I don't have pictures of them yet.

Probably a Japanese Master System cart, they had 22 pins on a side.  Same pinout as the SG-1000 (and SG 1k II) and Mk3.  Cart shape was the same as a colectovision, they used the same mold.