The white M-2795 shown in the photo is the only known specimen. It has Fred Locke incuse marking #4-1 on one side of the porcelain top skirt with the manufacturing date, DEC 7 1900, on the opposite side. The porcelain collar under the top skirt was glazewelded to the top skirt. The bottom glass skirt was made by the Brookfield Glass Co. It has the following embossed marking: LOCKE'S PAT'S / DEC. 15-96 JUNE 7-98. Note how the top skirt fits crooked on the glass bottom skirt. The porcelain collar was broken, glued back, and has no pieces missing. I suspect there was a small amount of sulfur cement remaining in the top of the collar that was too difficult to safely remove and prevents the porcelain top from resting evenly on the glass bottom skirt.
The two Fred Locke porcelain insulators to the right are very rare. Both are 2-part glazeweld styles manufactured according to Fred Locke's patent No. 852,730 granted on May 7, 1907. The one on the right is U-957. It has the incuse marking #7-1 on the top skirt which contains seven Fred Locke patent dates. Only two marked specimens are known and eight unmarked specimens have been reported.
The insulator on the left is U-957A and it is the only known specimen. It has Fred Locke's incuse marking #7-1 on the top skirt. Fred Locke's 83-year old granddaughter, Inez Locke, had it in her home when I visited her in 1993. She was using it upside-down as a pencil holder. She later accidentally knocked it over and the bottom skirt broke in several large pieces. Her older sister, Virginia Norton, sent it to me as a gift after Inez's death in 1997. You can see that the bottom skirt mended rather well.
Fred M. Locke dedicated web site