"Long Tom" became a generic name for long range, long bbled shotguns, mostly singles, around the turn of the last century.
There's plenty of these older models around. Most have steel bbls and cast iron receivers. Some are usable, but ALL old shotguns should be gone over by a competent smith before the very first shot is fired. Even then, I might tie it to a tree and use a long string to get the first shot or 5 off.
And if usable, this is a place for the low pressure loads now becoming common,like 7/8 oz in 12 gauge.CAS loads should do OK.
All that aside, there's something about easing through some hardwoods with one of these, with eyes cast up into the canopy, looking for that grey flash,and ears straining for the sound of acorns dropping. Or, partnering with a beagle and kicking brushpiles. A pocket of shells and a pleasing weight in the back of the vest can really make a monring...