As a side note, the "summer post office" at Acahela, PA was in operation from 07/08/1930 to 10/31/1944 according to this link (which is in line with the Postal Bulletin postings):
http://webpmt.usps.gov/pmt007.cfm?P...PENNSYLVANIAEven Jim Forte's Postal History Website has it wrong, as they show it in operation only from 1930-1941.
In either case, a post office only open for 14 summers has to be a relatively scarce postmark. I would agree the postcard shown is noting the new postmark handstamp (a nice clear one at that) put into use at that location, probably to replace a lost or damaged one that was in use earlier.