I last visited Sharnbrook just over a year ago and took a photograph of Sharnbrook's Midland signal box then but in cloudy conditions and from a different angle to this one, see.....
https://www.ontheupfast.com/p/21936chg/26818863804/sharnbrook-signal-box I must have figured that a bit of summer sunshine warranted another Kodachrome slide being used for a second photgraph! Unfortunately, I still do not know its date of construction but I do know that it closed just under a year from the day of this visit.