wow, talk about a barn find. It has a little 'patina'.

Looks like it will clean up nicely, (although sometimes a photo doesn't tell the whole story).
That's actually an R5, not an RD350. The R5 models were the predecessor to the RD350's that started production in 1973. The R5 is piston port while the RD is reed valve.
You can decode the year by the VIN/Engine #.
Engine or Frame Numbers (start-end)
1970 R5(A): R5-000101 - 013649
1971 R5B: R5-015101 - 042209
1972 R5C: R5-100101 - 130606
I'm guessing it's a '70. Paint colors were as follows:
1970 R5(A) - Metallic Purple/white
1971 R5B - Mandarin Orange/white
1972 R5C - Mandarin Orange/black
You're going to want to clean the carbs thoroughly, rinse out the fuel tank and flush the oiling system. It will probably need new engine seals too, and maybe carb boots.
Looks like it's all there. I only see a broken rear signal lens and missing left mirror. It's got an aftermarket seat, sissy-bar, and crash-bar.
Good luck, and congrats!