Thanks for all of your comments. Sorry that I did not thank you sooner, but I have been having some difficulty signing in. Malcolm, I also saw your comments in a different thread (and Alan Day mentioned the same to me) regarding what a bad idea it is to hold the concertina by a strap and let gravity do its dirtiest. I will furthermore eschew that practice!
I did take my life (and screw driver) in my hands and removed the right end from which I can detect air escaping. It SEEMS to be a pad, but all of the buttons seemed to be equally tensioned. All of the holes seem to be covered. Blowing through the holes from the other side of the pad does not seem to allow any air to escape.
I imagine I am going to have to send the instrument back to Colin to check. In any case, the left hand D, middle row, and E buttons in an unrelated matter, are producing some kind of slight metallic buzz or vibration. I imagine something was slightly dislodged in shipping.
By the way, regardless of these minor adjustments which need to be made, this is a wonderful instrument and I can hardly put it down. It is a dream to play, and quite beautiful to look at. My wife is filing for divorce claiming concertinadultery .
Thanks again for all of the assistance.