Just had a collector friend text me an example of a pre-1910 Conlon with borders that comes directly from Henry Yee's (PSA) vast database (he has others as well).
I believe you can tell it's pre-1910 based on Conlon's New Jersey address on the stamp. Apparently they are rare but do exist.
I'd feel 100% comfortable bidding on the Cobb as described by both REA and PSA after seeing this (if it were in my price range of course).