APO 858 hand cancel used on Simiutak (BW-3) - by Gale Raymond, Ice Cap News 1991:

"I didn't even try to reach Simiutak, accessible on its tiny rock-ledge only by a small supply boat or a rare helicopter, which sometimes also making a stop at Narssak point, a 4-man weather station halfway down the fjord. Simiutak had perhaps 25 or 30 men, including one officer.
I was told letters were picked up haphazardly by happenstance, and taken back to BW-1 for postmarking and fly-out. On even more rare occasions, and dependant on ice and weather, an icebreaker or supply-boat going "out" or "homeward-bound" would stop by or snatch-up mail.

At some point Simiutak was designated as APO 858-1, a branch of APO 858 still at BW-1. It is doubtful if Simiutak mail was ever cancelled other than at the main APO. In 1954, I wrote the Officer-in-Charge at Simiutak, a capt. R. H. Shea, AACS Detachment 1935-1, re a possible cancel there. Shaking down the Orderly Room, he found an old hand cancel, year date missing, which appeared never to have touched ink! Experimentally, he cancelled two covers to me of a May 5 date, 858, of the 4-bar hand cancel.
In a chatty letter, he suggested it may have been issued to cancel mail opportunely going out directly "homebound" to USA or a major supply-base in Newfoundland, by sea.
About one year later, I again wrote to the current Officer-in-Charge, who wrote that the cancel and a lot of other things had been phased-out and returned to BW-1, where all mail was routinely cancelled by them."