Good evening,
I would say late 20s to 40s. Spats came in 2 versions, the loose ones which were worn over the shoes, usually worn by young toffs etc. Or the type which is actually part of the uppers of the shoes which is what appears to be in the photo. Often known as gangster shoes, look at any old film of that era and you will see the mob bosses wearing them in the USA, Al Capone being one of them.
John915
PS As well as a riding crop he is also holding riding gloves and hat so must have changed hats for the photo.
PPS found these as an example;