This brown envelope from the Animal Health Review was posted to my father on the first day of issue of the commemorative stamps for the Silver wedding of Queen Elizabeth and the Duke of Edinburgh 1947-1972
It has 2 x 3p stamps, franked first day of issue 20 Nov 1972
The envelope, originally sent to the RVC at Brookman's Park, was opened.

I am including the contents, the first edition of Animal Health Review by Parke-Davis Autumn 1972, 
Hoping this might be of interest to someone, either for the stamp or the veterinary interest.

I have a second one of these envelopes for sale separately with the commemorative crown issued at the same time.