These are copied from the 5204 EPROMs in the personality module of several working Sol-20 computers. 

4-1 S0 goes in location U1, 4-1 S1 goes in U2, 4-1 S2 goes in U3, and 4-1 S3 goes in U4. 

The S1 BOOT EPROM replaces the 4-1 S1 EPROM in U2 to provide the BO (boot) command for booting from the Helios disk. You loose the TE terminal command with this EPROM.