Thanks to both of you. In the process of finding an answer I also learned a lot more about my car than I'd expected.
On MBDoc's tip, I started to wonder if someone had added the stepped washer as a spacer. I tracked down the MB mechanic the previous owner said had worked on the car, hoping to ask him whether there was some reason he had to raise the engine an inch or so.
He said he'd never met the previous owner (it's a small town and he remembers practically every car and owner he's serviced), but he did know the car. Evidently it was purchased new in Europe by a Department of Forestry official, who sold it to the guy I bought it from. He said the original owner took very good care of the car, so it's probably in pretty good shape.
He doesn't recall doing anything special to the motor mount, and suspects that someone may have added the spacers later to make the fan clear the shroud (as MB Doc suggests).
I thought maybe I'd give it the DIY try and replace the broken washer with a spacer of equal size, but after an hour or so of struggling to raise and position the engine with a floor jack and a 2 x 12, I realize that I don't have the tools to get that mount bolt back into place.
Instead I decided to go ahead and take it to the mechanic, who was after all very helpful. He can't look at it for a week and a half, so I'll be driving around in a "classic" '82 Chevy Chevette until my MB is back on the road. BTW, if you ever want a nice contrast, slide into a Chevette after driving around in a vintage MB for a few months. Aaaaahhh.. the smell of cat urine...the feel of pot metal and vinyl...takes me back...
I plan to have him check out some other stuff to, such as why the beast gets 8mpg when it seems to be running like a top.
BTW, my original post said my "118", which was a typo obviously. This is a classic 108.
Many thanks again.