All the literature I have says that when the Winnipeg Grenadines were in Jamaica the air mail postage rate to Canada was 1 shilling / ounce. This letter from Captain Gresham to Winnipeg is paid at only 10 pence.
The BNAPS Military Mail study Group newsletter issue 51 has an illustration of another example paid at 10 pence.
The article in the Forces Postal History Society Journal No 325 page 275 also has 2 covers from Gresham paid at 10 pence.
I am assuming that these were underpaid in error and allowed to pass through the post without postage due.
Unless anyone knows better.
John
I have a number of covers from Capt Gresham, all airmail and all with 10d postage. I have other airmail with 1s but others still with 6d. I have endeavoured to find any mention of postal rates but so far without success.
Did the rates change over the passage of time? Can you point me at your sources?
Are you a member of the Canadian Military Mail Study Group? If so, it might be worth asking the question of them. If not, I should be pleased to do so
Alan
I have just read your second reply. See attached screen shout of a spreadsheet index I try to keep of literature references. I hope you can read it and it helps.
John