Things Found

Today I was staring at the bookshelf and idly pulled this one out... Can't even remember when I bought it, it's been so long since I looked at it last. Weird thing is, I found a letter in it that I don't recall being there. It's an instructive letter on scraperboard, typewritten, not by the author above, but by an illustrator named Edward S. Billin.
I found a example or two of his work, from a book published in 1952 called "Drawing on Scraper-board" and have scanned the letter for you to read below.
It sounds like something that would have been sent through the Famous Artists Painting Course, but there are no examples, no notes or drawings.
Enjoy - especially my students - most of whom have never heard of this medium!