Much appreciated on that effort. A little hard to tell, but it looks like that other black plastic oval (standard issue) RV plate isn't on the back. No loss about that, if it is missing. Could be I'm thinking of vinyl stickers that Ed Black's might have had instead of Galles. My dad bought his '86-ish regular pickup from those guys. More often that not, most Chalets & GMC Casa Grandes I run across have no dealer logos on the back, but some have the potmetal logos and others have vinyl ones.
On the $20k Chalet, that was Chalet #1385, an anomaly that might have over-inflated the classic dealer prices of one or two others. #1385 was on ebay and had multiple bidders up to the $10 grand point, but then just the remaining individual who took it on up to the reserve of $21,500. I saved the bidders history printout on that one. From what I've seen of others in really good shape (near showroom-new restorations), the high-end value of these tops out at around $12-$15 grand. I go into a bit more detail on that in the "Buying And Selling" section of the blazerchalet.com page
here. (I'm the caretaker of that site, nearly all of the other content was put in there by its creators years ago)