Sorry, mis-wrote the number. Thanks for the ROM image.
Unfortunately this is the exact same as mine, detok still reports a bad checksum:
$ detok 525_1351_02.bin |head
version1 ( 8-bit offsets)
format: 0x03
checksum should be: 0x2eef, but is 0x2f02
len: 0x3adc ( 15068 bytes)...
I've got a Sun Sbus quad ethernet adapter (X1058A, 501-2602) that I booted in my Sparcstation IPX and Sparcstation 20. Both report "Invalid fcode start byte". It seems my ROM is corrupt.
I went ahead and dumped the ROM, and ran 'detok' (from fcode-utils) to translate the binary back to forth...