Frederic Remington 1961 First Day of Issue Cover

I recently pulled out my old stamp collection from 50 years ago and was doing some research on some old stamps. I came across this Frederic Remington First Day of Issue Cover from 1961. I knew something wasn't right when a corrected version of his name kept popping up while I was researching online. I then realized that his name was misspelled on the First Day of Issue cover which had added a 'K' to the end of Frederic's name and spelling it as 'Frederick' instead of 'Frederic'.

I tried doing some research but I couldn't find any info on this particular cover so I'm not sure if it was pulled from circulation or not. I can't find a single picture or mention about this cover. This First Day of Issue cover is authentic because my mother purchased it from the post office next door to where she worked at the time so it wasn't purchased from a dealer or purchased online. Also pictured is the back of the cover which of course does show that the glue has penetrated through but the cover is in excellent condition and still in tact.

I hope someone can provide more info about this particular Frederic(k) Remington 1961 First Day of Issue Cover with the cancelled 4 cent stamp and tell me what it might be worth?

Much appreciated!!