I don't know much about Gray payphones or even payphones in general, but is a Gray with a bulldog transmitter cause for concern?
I found my answer (http://www.classicrotaryphones.com/forum/index.php?topic=6139.0 (http://www.classicrotaryphones.com/forum/index.php?topic=6139.0)), so I will modify the question. When did they go from cone to bulldog on Gray paystations?
I think it came out on 150Gs (replacing the 50G) from the factory towards the end of Gray's run. I don't know any dates, but Gray never issued handset models from the factory, AFAIK, so the Bulldog models (antisidetone) would have to have been the last general model in Gray's existence (in short, I would guess they were used from around the time antisidetone became common up until 1948, when Gray was sold to AECo).
Not much at all, but I'll just let the Pay Station experts tell you.