Your programmer can read the manufacturer ID from the chip?
Is possible the chip are "fake new" chip from China. If the manufacturer ID don't match with the printed ID then it is 100% fake.
If same ID then you can't sure about it.
The problem: at the "fake new" chips you can't sure about the access time. Too slow chip can make problem with Enterprise.
What is the chip size in the EPROM window? The modern (max 20 years old
EPROMs are very small. Older ones are about half size of the windows, more older about full size.
I used many M27C256B with Enterprise, without problem.