Some of the things that changed throughout the 72-73 models:
- early 72s had chrome shifter plates, late 72 and later have plastic
- 72 and early 73 have chrome rings around the horn buttons
- 72 (up to some point) had a 350sl badge, and 73 got the 450sl badge, even though both 72 and early 73 both have the 117.962 motor.
- 72 and early 73 have brass radiator overflows, and late 73 got plastic
EDIT: I THINK the following are true too:
- Very Late 1973 had the cluster change and no center vent clock
- Very Late 1973 got one-piece seat belts I believe (but still had small bumpers)
- Late 1973 got ribbed, integrated, horn buttons on the steering wheel
- Some 72s have manual windows while it appears all 73s have power.

Any others?

I would think any other early-72-only features like the chrome shifter plates would make an early 72 more desirable, including the 350sl badge, even if it wasn't correct. These are things that a true enthusiast-collector will understand, but folks like deanyal (is that denial?) might mistake for more important features.

If the car is an early VIN that should have had a chrome shifter plate, and a 350SL badge, it is easy enough to find those and install them to make the car "factory-correct" if that's what you'd like.

I am an early-73 owner, and I've installed a chrome shifter plate, just because I like it, and I could. I keep the original in the trunk in a plastic bad with a note that explains what I did in the event I die before the car does.