Help date university blazer please?

[Sartorial Eloquence]

I recently bought this old blazer in a charity shop but I have very little idea of its age. I Googled the company Rowans of Glasgow and Birmingham but didn't find out much except that it was apparently established circa 1846, which doesn't narrow it down much! The crest which appears on the pocket and metal buttons belongs to the University of Glasgow (which is older than Rowans). Any ideas? There are no labels other than the two Rowans ones on and in the inside pocket which I've photographed.

Thanks,

Irene