Many of the CBM-II machines, especially the high profile models, use 28 pin 2764 EPROMS.  Since the sockets for the Kernal and Basic ROMs are 24 pin, adaptors are necessary to use these EPROMs.  Here is the adaptor configuration:

28 24
1  24
2  21
3  1
4  2
5  3
6  4
7  5
8  6
9  7
10 8
11 9
12 10
13 11
14 12
15 13
16 14
17 15
18 16
19 17
20 12
21 19
22 20
23 18
24 22
25 23
26 24
27 24
28 24