Sockets
There isn't much space in cartridges, so developers had to use low-profile sockets to hold the EPROMs in cartridges.
(Among others?), KEL's ICC12 (datasheet) line of sockets was used.
It seems 3M's 400 series (datasheet) is the same. Did 3M buy KEL's ICC12 series?
In mid-1999, due to the discontinuance of KEL's ICC12 series, SNK switched to Omron XR2 sockets, which are still available to these days. (https://components.omron.com/us-en/products/connectors/XR2)