the Matchless twin engine responds well to a knowledgeable mechanic but doesn't cope well with enthusiastic amateurs.
hahahahahahaa, thats one way to put it...
Im in australia and ive been noticing prices of these bikes sky-rocketing over the past year or two - as for this situation, it would be an excellent buy for less than $1000
as a restoration its desirable because it does appear to have all the necessary bits, whether original or otherwise. it has a speedo, which, if an original Smiths, is worth big $$$ in itself; it appears to have a magneto, a bonus; tank and tinware are all present and repairable
think of it this way - if you want to spend a lot of money restoring it, its a good start for roughly >$1,000, but youll be a few thousand under by the end of the job. especially because those matchless twins are renowned for terrible oil circulation problems. ergo, youll want to consider roller-bearing conversions and the like - more $$$.
to me - not a big AMC twin fan - its not worth the headache. but if you have deeeeep full pockets and a love for matchys, itd be a fun project
still, only my opinion