For your consideration are 2 documents (rare pieces of Britiish history)
1- MILITARY DOCUMENT : GRANT OF THE DIGNITY signed by King Edward VIII Signed as Grand Master Prince Wales Windsor “Edward P,” dated 3 June 1919. document measures approximately 12.75" × 15.25" when opened up. It has a raised seal. In this Document King George V appoints John Howard Slayter to temporary Captain of the Medical corps of the forces of our dominion of Canada
NOT SURE if Certificate is hand-signed by H.M. King George V or a facsimile signature of the king.
(It looks authentic but I am not a pro at this. We aquired our Royal collectible collection through elderly relatives of the collector who passed on. She just wanted a garage full of treasures gone and we were blessed to receive the amazing treasures.)
2- A letter dated 22 November 1920 ( I believe this goes along with the other document -Grant of the Dignity. The Letterhead reads:
CENTRAL CHANCERY OF THE ORDERS OF KNIGHTHOOD - ST. JAMES PALACE S.W.1 - It mentions Major J.H. Slayter