DB I bought it when I was an undergraduate in Cambridge, at the actual Filene's Basement. If I could travel back in time, I'd have my past self size down one, but for a clueless freshman, I didn't do so bad, I think. Here are some other pics. It's 80s Givenchy, which was not a good time for the French men's fashion houses, but the cloth is really nice:
Comments on the aesthetic will be of interest.
To me it looks like a cross between a classic raglan and polo coat, and perhaps also related to trenchcoats. I recall the raglan sleeve was designed to be more water resistant.
There is a picture of another similar variant in a trenchcoat.
I think the drape, accentuated by the belt, is how traditional polo coats are supposed to look.
Here is a bespoke polo coat by Despos.
I think you have a great find and I would wear it just as it is. It looks roomy but also good when compared with other leaner versions above.
Too bad I never went to Filene's. I had friends who waxed poetic about Filene's but I was not interested in clothing those days. I have 4m of a barleycorn donegal that I plan to make up one day with a raglan collar and sleeves. This gives me ideas on what other details to consider.
I was back in Cambridge last year and it has gentrified quite a bit. Central Square and Inman square have really cleaned up.