It's gorgeous, it's a little hard to tell the intended shape without the contrast of skin underneath. If you can get some photos taken of you modelling it that would be very helpful.
First of all zips are rare in 1930s garments and a relatively new concept at the time. They also don't get to the back of a garment until later (generally 50's) My first impression was 1970s, as it has that medieval Guinevere look to it. The only dress I have had with the same slashed chiffon balloon sleeves is of the late 60's-70's era, but the zip appears older (40s/50s style) of course it could be homemade with old supplies.
The lining of the sheer back with nude net does appear to be and older technique, I can't recall seeing this on later 20thC garments.
Personally, I would hesistate to donate something this delicate to an amateur arts group, for all the good intentions it isn't going to last in such prestine condition for as long as it might elsewhere. A local museum may well be interested, but more so if you had any information to go with it.
