|Round round, get around, I get a round.|
Well some people just have to be different and in the case of searchlights this means the interesting case of the non-round target. Typically associated with the Chicago Northwestern Railway, oval searchlight targets could also be found on certain parts of the CSX system in what I think was the old L&N territory. The reason the CNW is known for them is that this style of searchlight appeared at many famous railfaning locations including TOWER A-2 and JB tower in Chicago, in near classic coaling tower in Nelson, IL and at the Rochelle, IL railfan park.
|Tower A-2, Clear eastbound on the CNW West Line|
The oval searchlights were a US&S product, but don't think that US&S only sold this type of searchlight as they were more than happy to sell the default round backing for their H-2 and H-5 searchlight offerings. As far as I can tell, the oval backings were a modification of the backing for N-2 style color light signals as seen here in their intended function.
So why go oval? In the case of the CNW, much of their signaling involved (sometimes sideways) GRS color light signals with a mid-sized oval backing and the oval searchlights would provide a similar look and feel. On the L&N their standard signal was the US&S N-series so again, an oval backing would match. This theory is given credence by this photo of searchlights in former C&O territory near Toledo. The C&O was almost exclusively a user of US&S N-series color lights.
Of course in other situations the oval backing may have been used for clearance or line-of-sight reasons, like this example in the wilds of Tennessee. I can't tell if these are simply chopped down N-2 backings or something with completely different dimensions. I suspect they are simply trimmed down on the sides.
I'll leave you with another photo taken in 1955 that shows the CNW didn't save the oval searchlights just for interlockings. Here we see a UP passenger train rushing past a pair of what look to be brand new CTC signals on the CNW Galena Division between West Chicago and Nelson. All 8 searchlight heads are fitted with oval backing plates. I am uncertain how much CNW territory got these signals and how long they lasted, but it goes to show that oval searchlights can always pop up where you don't expect them.