I've finally gotten as much info on this book as I'm ever going to get (barring a dust jacket mysteriously appearing out of the sky). It's done.
Now I have to catalogue it. Then life will get back to normal again. (until the next time I get lost in the details).
I want to thank everyone who helped me finally figure out what I have.
The people at the Shel Silverstein website were awesome.
As was Christy Hicks at the Arne Nixon Center at Calif State University at Fresno (did you know there was a special collection at Fresno State of picture books? FRESNO! And today I found out that Fresno has the third largest library in the Cal. State system .... FRESNO! )
a whole boatload of people on the Biblio newsgroup who volunteered bits of information.
I'm hoping I won't be bothering them all again soon.
PS: in the end, I can notate this book as a first printing, but there's no way to designate it as a first printing without the dust jacket. And I was correct that people were generally mistaking later reprint copies (which are in lightish brown full cloth bindings with gilt lettering) as first editions.
The book will go up on my website as soon as I get a chance.