Tom & All
My Remington-Rand brain computes the following:
The 1915 Val Inventory did not list an interlocking tower which was all that was available when I prepared the 1997 Tour Guidebook.
Later Cookie provided a 1935 (and later) inventories of the property which had the following:
Haskells, Item 4. Interlocking tower; Kind: Frame-Stucco; Built: 1917 by AFE #365; 33 1/3% CI&L Ownership. (only information shown)
The interlocking replacing Gates was first shown in CIL ETT #36 effective 11/05/1916 indicating the interlocking became operational after 10/03/15 the effective date onf ETT # 35.
The dates do not seem to compute, but that is all the official (or unofficial) data I have on hand.