Crumb is discussing, of course, the quite infamous first issue of Zap Comics! Woody, being Woody, was likely ordering 25 copies of one of the most famous underground comix ever published to distribute to his friends and colleagues. Currently that's something on the order of a half million dollars worth of pulp that Woody got for a mere $3.75! There is some good information in this letter concerning the print run of the first issue's first run, which would be in excess of 3,500 copies a figure toward the upper end of estimates for this historical artifact. It would appear 4,000 to 5,000 first edition copies would have been run I think. It also appears Woody had received copies previously.
You also get wind of Crumb's firstborn, Jesse; the search for a New York distributor; and a query as to whether Bhob Stewart (the longtime reviewer at Publishers Weekly and generally a comics historian) had seen the first issue.
The fact that Woody's response is also extant is quite remarkable, although I suspect it was a carbon. Woody also had a file going on Crumb in his archives:
I love the Nostalgia Press letterhead! I also get the distinct impression Crumb and his (first) wife had visited Woody recently at his home in Malverne, Long Island, NY. Woody's handwriting is atrocious, worse than mine even, and I can't make everything out (there is some sort of "familiar" abbreviation to boot ) but Woody definitely showed Zap #1 to a very young Art Spiegelman, which is kind of mind blowing! Let's not overlook that $20 gift to young Jesse Crumb either-these guys were clearly friends.
Woody was a prime mover in subversive comic art and the extent of his involvement and appreciation in the movement seems to grow every time another bit of information is uncovered. And this all needs to be put into historical perspective as Woody was writing back to Crumb two weeks after Martin Luther King was murdered. It was a chaotic time in America.