Well, the serial number format is consistent with Miyata and if we assume it's Miyata, then it would be circa 1973/1974, which matches the seller's claim and is apprpriate for the Crane rear derailleur. However, I have not seen those lugs and stay tips on Miyata from this period, but if this is a contract manufactured frame, the lugs and stays tips may be customer specified. The Falk tubing is an Italian brand, comparable to Columbus. It would seem to be stretching things a bit to assume Miyata would be using this, but stranger things have happened, so I won't rule out the possibility.

There seems to be some remains of a tubing decal, below the seat lug. Can you post a pic?