I would have guessed late 60's myself given the headset mounted lamp bracket (which is installed upside down).
Also, Diacompe copied Weinmann designed brakes and manufactured them under license. I typically never see the hypenated brand name on later 70's issues. Still, the backside of the calipers might lend a clue as to its age, as most are dated.

I would think this is pretty early to see a Silk bike in the US. Based on the plain lugs and what looks like a stamped fork crown cap, I would say this was an entry level bike, not to the standard of their later offerings. The level of components if they are original supports that, and the black repaint devalues the bike. In its current state it has very little value.

If you are inclined to work on it it might clean up alright, but it will be a lot of work, and you will have to spring for a new saddle, chain and FW at least. Before you even consider it make sure the stem and seatpost are moveable.