I got this Locke #21 the other day t off eBay. When it arrived I realizes I had something interesting . It clearly is a very early production of this piece in the typical light aqua Brookfield made in the 1898-1903 era . I have actually never seen an early light aqua example like this before in the large pinholle with the "FM" not blotted out and have been looking for one for a long time . . This example was made in an obviously new mould . The mould lines are tight and the mould machining is very visible and it could well be from the very first production run of this insulator . Most of these I see in collections are in the avrage to darker aqua shades typical of later Brookfield (post- Fred Locke production ) In Fred Locke's early catalouges these were listed as available only with 1 3/8 threads . In the December 1904 catalogue that was issued just after Fred departed the Locke company they were for the first time with standard 1" threads as cat # 22. and also as before with the larger pin hole as cat #21. Virtually every example I have ever seen has 1" threas and is the later darker aqua . My guess is this one is a real Fred Locke example made when he controlled the company where as the others are mostly later examples sold by Victor in the 1905-1915 time frame .