Ordered a letter today for a Model 53, 6", blue, 4 screw. It shipped in May 1961.
Have read a lot of threads about are letters worth it.
I have decided not to worry about the cost or if the letter will be something other than garden variety.
I'm going to consider it as a donation to SWHF. We should all be doing that anyway if we can.
So, I make a small donation to SWHF and get a free letter out of the deal. Sweet.