I now have a dump that should be right.
It was an issue with the breadboard. Another one worked at once.
The ROM contents are strange. No strings (in either encoding) and no PDP-8 code. Values in octal are too high.
Some large sections are 00 and 0F00. Would make sense as a binary pattern. Parts of the EPROM could be defective.
The first 2 bytes are 05 00 hex. Could be the length (500 bytes, 5 lines or 5 words) or a magic bytes header or checksum. Or the start adress of the other 8 ROM code. When I remove that and adding 2 bytes after byte 14, I got a plausible pattern. Most plausible are lines of 16 hex-bytes or 2.
4 lines of 16 bytes starting with 01 03.
Then 2x2 lines 02 00 58 9C 53, rest 00, and one line with 00 each.
05 00
01 03 01 93 02 10 02 10 25 9C 23 40 00 00 00 00
01 03 01 93 02 13 03 93 02 40 00 00 00 00 00 00
02 00 58 9C 53 00 00 00 00 00 00 00 00 00 00 00
The main appearing data starting at 80 (hex) consisting of 2x2 rows and a very similar pattern at 0180.
58 1C 54 5C 56 30 04 33 06 73 04 73 26 3C 24 3C
58 1C 54 5C 56 3C 24 7C 26 3C 24 3C 0F 00 0F 00
18 16 14 56 16 10 08 10 0F 00 0F 00 0F 00 0F 00
18 16 14 56 16 56 19 3C 54 7C 56 3C 54 3C 0F 00
C0-FF all 00
100-17F and 1C0-1FF:
00 00 0F 00 0F 00 0F 00 0F 00 0F 00 0F 00 0F 00
at 0180
58 10 54 50 56 30 04 30 06 70 04 70 0F 00 0F 00
Some of these lines when removing 0f00 have 8 bytes, others 12 bytes.
Does all this make sense to anyone?
The beginning is maybe similar like Intel HEX?
It’s also possible that pins are swapped and contents scrambled.
Or pattern for audio tape. Or discrete CPU.
As there are no strings, it means that they must be in the other 8 ROMs.
So most likely encrypted.