By the chip capacity on the flashboards is the technical way. Over the years, I've learned to identify basically by looking at the chips. Most intel flash nands are 128MB boards, but there some 256 boards, I believe the 128MB boards have physically smaller chips than the 128's. I will have to look at some boards I have around that are bad (hoping to be able to fix them one day). I will see if I can post what most 128MB boards look like. 99% of the 128MB boards have been of the brown variety, with the green ones usually 256MB.
The other way is by the program flashed in them. If you post the firmware ID, I might be able to look it up on my notes that I have accumulated over the years.