Oh sure, I think I've heard of that before, now that you mention it...
You will also occasionally find cross peen hammers with a rather large round hole in the peen end.
These were used to install the "pegs" that we're screwed into the poles for the lineman to climb on.
I'm sure "pegs"isn't the correct term,but it's the best I could come up with. They are actually a lag bolt affair with a bent up end that you slipped the hole in the hammer over so you could turn it into the pole.
For whatever reason, I see more of the square hole hatchets than the hammers. All the hatchets I've run across have been marked "Bell System". Under the rust yours is probably marked that way too.
Mike
Yep, I had one of the hammers in the past. But, I bought it specifically to resell it :P Was a nice lookin' hammer though...
Not sure what else may be marked on it, I'm not able to physically examine it. But, I'm sure it probably does have Bell System stamped into it, like all their other specialty tools.
Thanks!