Just in case some of you have been unable to sleep at night without knowing the name of this business college, I believe that I have figured it out.
Another extremely crude "stamp" appeared recently. It doesn't appear at first to look similar to the first one that I showed. But if you look close, it does have a similar, barely-readable cancel on it.
The cancel is a bit more readable once it's been processed by postmark-reveal.
The "lin's" was sort of readable on the first stamp, and something that sort of looks like "dev" is at the top left on this second stamp.
I spent several minutes squinting at this image and flipping it and all sorts of other things.
With fingers crossed, I googled "Devlin's Business College."
And, lo and behold, the "city" portion that can be seen on both stamps suddenly makes sense, and what looks like the "bay" on the first one also makes sense.
Thought that you'd like to know that this particular mystery has been solved!
p.s. What on earth is that thing in the center? A bird with three wings? A pigeon with a giant rudder?