no doubt a Russian lend lease valentine, apparently the Russians really liked the valentine for it's low silhouette and quiet running. I once read an account about 2 Russian valentines stalking a tiger in the long grass of the steppes and getting the kill.
last year I had the chance to drive a friends valentine and was surprised at what a nice tank it was to drive, it had plenty of power in the turn so you didn't need to rev the nuts off it, also had synchro mesh in 3rd and 4th which is rare to find in a tank gearbox. (not as nice as a Cromwell though)
Great job figuring this one out...I hadn't thought of Lend-Lease...The centered vision-slit was a mystery to me, lol...