How was this Locke insulator used? Here is a comparison photo of the Locke glass sleeve on the right and the similar looking Pyrex stacker sleeve CD 311 on the left. Further notes: The Locke sleeve's latest patent date is October 12, 1915. This particular Pyrex stacker sleeve has Corning's Pyrex patent date of May 27, 1919. The Pyrex stackers were not installed in Montana until about 1923.

The Cochrane Bells suspension post-date the Locke sleeve by almost a year. [id=676735404]