The special printings of 1935 are somewhat exotic in the otherwise rather plain and predictable stamp issues of the USA. Usually I collect USA used,missing all expensive stamps. The special printing souvenir sheets were printed in rather small quantities.They were printed and sold (also) in complete sheets of nine. To collect them in full sheets might be quite costly,I suppose.Let alone to find a fitting album for them. Although so few were printed,the sheets still are affordable. So I looked for and found the sheets (mint) in pairs for a relative moderate price. Here (attached) Scott no.766,issued,like all others,on March 15th,1935. They were sold for three months,till June 15th. 98.712 were printed,less than the 107.398 of the White Plains s.s. (Sc.630) of 1926.A fine example,that not a low printing quantity alone guarantees a high price.But popularity,or the lack of it,is important as well.
They're quite attractive! Agree that popularity is part of the valuation equation. The White Plains sheet took off right away and never came back. The full story of the Farleys ('Farley's Follies') is quite interesting. Here's a little about them: https://www.apfelbauminc.com/blog/farleys-follies Ralph Sloat penned an entire book on them.
Sc.767 is the USA souvenir sheet with the lowest printing quantity. Just 85.914 were printed.It is valued so cheap,that it is hard to believe,if you are used to the prices of souvenir sheets from Germany.
Had heard the Farley story, but in a little less detail. They're fascinating stamps for sure, and I was inspired / motivated enough to obtain at least the souvenir sheets and gutter pairs. Then in a fit of insanity, collected the mint plate blocks of both the perf and imperf varieties of the parks issues. Kick myself to this day for passing on the purchase of a complete set of mint sheets of the perforated parks.