HR Harmer Auctions, Sale 3033, August 6, 2020 has ten (10) Guatemala stamp and postal history lots in their current auction.
Their main website:
www.hrharmer.com
Here is the search that should get you to the Guatemala collections:
https://hrharmer.com/en/_auctions/?action=search&auctionID=33&cd=eJyrVipOTSxKzlCyUkovTSxJzU3MSVSqBQBZ0Qfi&search_submit=1
Eric Dyck
Librarian and Website Administrator
ISGC