There are two distinct Variations of the M-2332. In the 1902 Locke catalog the #307 is listed as having a diameter of 7 1/2 " which corresponds to the left specimen. The 1904 Locke catalog has this insulator listed with a diameter of 7 3/8 " which is the diameter of the right one. The left specimen has a full mold line extending from skirt edge to skirt edge. This is normally found only on multiparts produced in 1902 and early 1903. The right insulator has what I call a reverse three part mold which has a mold line over the dome and a mold line line or raised ridge circling the crown. This is found on 1903-05 era insulators. See the next photo for a top view of these.
The M-2332 was well documented by long time collector Robert Winkler. According to him, this insulator was the favorite choice of interurban railroad builders in the midwest from 1902 to 1907 and they were being installed that late. They were once as common as a Hemingray 42 on the early electric railways of the midwest.. The tan unit is now owned by Reed Thorn a very enthusiastic mud collector!