Seamus, that's a great find, especially with the original bag.
I wouldn't say that 638s are hard to find generally but you seldom see one in that sort of condition.
Re: the scratches I've managed quite well by rubbing down with progressively finer grades of abrasive paper, followed by a coat of clear laquer aerosol. This has worked well for me on a number of plastics, including bakelite hoods, brings the shine back and doesn't leave any sticky residue. You can get these items from most car-accessory shops.
I'd be interested to hear about how the plastics-polishing kit works out.
Stephen