Looking at these two post cards, something struck me as kind of interesting. Both were mailed from Gloucester Mass. four days apart in 1937. Both from the same person, the mysterious S., with wonderful penmanship. Both to Mrs Soley in Wolfville NS. Both have #634 Washington's on them, perf 11x10.5. What I found odd was the difference in colour between the two stamps! One seems carmine, the other more of a carmine rose.
I know scans and monitors can make colour ID difficult, but I scanned both of these together, so you should be able to see the difference.
What do you figure? S. took a bunch of stamps with him/her on vacation, and they just happened to be different colours, or the local post office had a drawer full of these from a span of many years? These were issued from 1926 to 1934. They were sitting in the drawer at least 3 years?
I'm more interested in those enigmatic messages. "Made a circuit of this lake yesterday? S." Then four days later, "You have no doubt learned how I happened to be here last Sunday. S." One could weave a decent story around those. Did the knowledge of how S. came to that place spell doom for Mrs Minnie Soley? What horrors did Mrs. Soley see on her circuit of the lake? We may never know.
There are as far as I can see only listed as CARMINE for these, but if you have ID's them correctly then shade is left up to human error (Over-inking, and the like) or atmospheric factors. These seem to be a late usage of this stamp as in 1937 it was all about the National Park issues but the ones you show are definitive issues after all. Design of A157 and Scott #660, Rotary Printing. I hope this helps out a little?
NOTE: I see you had them I.D.'s as Scott #634. Why? (You may very well be correct) As you know without inspecting these "in-hand" it can be quite tricky to nail down a positive ID from a scan.