Originally Posted by
repechage
Nice fork crown, the image of the rear drive side dropout is not that detailed... the bike has had a long life of use, could an integral hanger been cut off?
The hanger could have been removed but the 1962 literature in which the 881/881B hangerless dropouts first appear, is also the first time that JUY SIMPLEX is shown on the dropouts. So, even if the hanger has been removed, the lettering would appear to be a dating tool. It should be very easy to tell is the hanger has been removed, by having the OP's friend examine the bottom on the drive side, rear dropout.
Also, while it could be a coincidence, there's a good probability that the lead '3' in the S/N is the year indicator. That was a very common practice and, if so, would indicate 1963 or 1973 manufacture, with 1963 seeming more appropriate.