OK so a quick update. RetroTech Chris did a video on his Youtube channel about Xircom network adapters so I reached out to him to do some EEPROM dumps. I'm going to leave the results here for future reference:
Adapter 1:
Manufactured on 12/04/1994 at 25:10:03
Raw EEPROM contents: 4328 2029 6958 6372 6d6f 3120 3939 2033 3f8e 0030 0a46 8293 3350 0054 c780 102f
Ethernet Address: 00:80:C8:30:3F:8E
Adapter 2:
Manufactured on 02/01/1993 at 25:50:36
Raw EEPROM contents: 4328 2029 6958 6372 6d6f 3120 3939 2033 2165 002e 0811 a39d 3350 0054 c780 0f85
Ethernet Address: 00:80:C8:2E:21:65
Adapter 3:
Manufactured on 23/05/1995 at 09:40:19
Raw EEPROM contents: 4328 2029 6958 6372 6d6f 3120 3939 2033 b44f 0030 8a5c 139a 3350 0054 c780 8a51
Ethernet Address: 00:80:C8:30:B5:4F
Adapter 4:
Manufactured on 09/04/1997 at 09:04:06
Raw EEPROM contents: 4328 2029 6958 6372 6d6f 3120 3939 2033 28a8 0030 8e45 691 3350 0054 c780 1f18
Ethernet Address: 00:80:C8:30:28:A8
EDIT:
So here was an example of my EEPROM code generator, which was missing some data:
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 7c d7 3b 00 84 3e e7 35 00 00 00 ab ca 85 14 83
So based on the dumps of the missing first 16 bytes, it is actually an ASCII string:
'(C) Xircom 1993'
And another missing word of data which is constant across the dumps is 'P3' in ASCII, maybe it stands for Pocket Ethernet 3?