Ever heard of or seen an Illinois 6540 strop

My pops has a strop that was his grandpas. The number appears to be 6540. wondering if anyone has ever seen one.
will try to post a pic tomorrow.

This strop must be pretty old if it was my great grandpas. he had to have been born around 1890 or 1900 as my grandpa was born in the 1920s and my dad 1950.

Dad has been using this strop for years for knives. it is still in fantastic shape (the leather side anyway). No real nicks to speak of, I must say the leather they used when it was made is of the highest quality i can imagine. still soft and supple and smooth and i dont think my dad really takes care of it all too well.
just wondering if anyone has any info on the number of strop i have.