I have a fine, fine, advanced Pickett brand aluminum slide rule (with log and trig functions, etc) in its leather case...and the sliding hairline is accurate, true, and moves freely. PM me and we can talk pricing.
BTW, after reading your query earlier, I went down to my local specialty pawn shop, and looked at a D50. They had it at $149 body only, and I examined it...as I recalled, it felt better-made than the D40 and later models...more "solid". The viewfinder image was not that big, but the camera itself...not too shabby.
Goodwill Industries has affordable cameras, 35mm SLR bodies and a 50mm lens, often $19.95 here on the west coast. 35mm film camera prices for SLRs are VERY low theses days. Former $1,000 Canon and Nikon F100's sell for $100-$140, and they sell slooooooooowly.