It is possible either competing companies operated along each side of the railroad trackage through this central Massachusetts town. Or maybe one was an older line in the process of being upgraded to a newer one on the other side?

At any rate, while out there hunting for insulators along old railroad right-of-way be sure to check and research EACH side of the RR right-of-way because you never know what once stood on the other side from where the existing line stands. Such opposite lines could have been taken out of service many, many years ago without a single trace of them remaining upon a quick glance today!

And that's where the oldest stuff is most likely to be found buried beneath the soil ;-)