Are you going to look in NH?
I think that is probably a forum member's car. Or at least nhdoc has one.
A 1981 TD never came with a manual. In fact, there wasn't a W123 OM617 produced with a manual ever. Probably a transmission from a 240D. Not a bad combo, but look out for vibrations unless shifting pretty high up the rpm range; the 240D flywheel isn't heavy enough to not drop the rpms fairly quickly between gears.
Look out for the normal things: rust, body damage, suspension, etc. It's too warm out now to really check the compression by doing a cold start, but check blowby. There's probably 500 threads on here where advice is given for looking at a new car. Service records are worth their weight in gold.

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