James, they aren't really Boston Store cards. The grading companies don't really have much of a clue as to what the designation is on these, and I don't know that I blame them as they really don't have a designation. For example M101-4's and 5's are the designation when blank backed, W575-1 is the designation when the E121 series is blank backed, but these have never really been catalogued. I personally have always simply referred to them as E135 Blank Backs, as they are likely a candy issue, but theoretically they could have come with anything.
Of all the E135-like backs the blank backs are certainly tugher than either E135 Collins-McCarthy's or the H801 Boston Store cards. They are more similar in difficulty to the D328 Weil and D350-2 Standard Biscuit cards. However, they have never really had the premium attachec to them as the latter two as they aren't as interesting. Also, the true E135 Blank backs all should be factory cut.
This, however, was a mistake by the grading company (which is more unforgivable than your examples):
Hope this helps,
-Rhett