
The serial nbr was on the front face of the receiver, as has been found and discussed. these were 37's with some short lived mods that simply didn't work out. the 87 was subsequently changed back to 37. The 87 is simply a year designator when the company resumed production (after a bancruptcy - or sale to a new owner, I would have to go read which, I simply don't remember). Which leads into the fact that there are later production guns with "37" in the serial nbr, ie: M37xxxxxxx and guns with "87" in the serial nbr, ie: MAG-87xxxxxxxx,

Ithaca added 1/4" to the receiver and selected components to allow the chambering/ejection of a 3" shell. measuring the receiver is another way to determine which shell the gun was set up for.

In time the word MAG was removed from the serial nbr. You can identify the switch over to the 3" receivers by the word MAG- as either a suffix or as a prefix. A 3" chambered barrel will fit and work fine on a 2 3/4" receiver but of course, can only chamber 2 3/4" shells. This is an immediate identification method that the gun is an interchangeable barrel model, keeping in mind that there are 2 3/4" receivers and 3" receivers. These are at the bottom right of the receiver, above the trigger guard. This is at the change to the way the barrels attached to the frame. Serial nbrs on Ithaca 37's should fall into this pattern
