There are differences in:
1. curvature of the triggers (one is a deeper curve than the other),
2. hammers,
3. hammer pins (one is a roll pin, the other and easy take-down),
4. the trigger bar spring assembly (may be a difference in the way the 4 pieces are held together, one used a tiny roll pin and the other used an easy slide pin),
5. the slide lock/release is different,
6. the safety levers (one has the hole that can make it easier to remove/reinstall the lever in reference to the safety detent) and
7. the barrel may or may not have the serial number stamped on it but that may be due to something else.
These are just some of the things I’ve noticed that may or may not be relevant. I really like the earlier version of the Series 88’s.
Oh, and I don’t know why, but I’ve seen some versions with the slanted slide serrations like these and some with “CZ” styled vertical slide serrations.