I have way too many projects but how are you supposed to pass on a early RT-1, especially if you never had one. Probably let this one go as I’m over my limit on space. Looks like a great candidate for restoration, needs everything as usual. It's titled, pristine gas tank inside and it came with a RT3 oil tank and oil pump. Engine case number is not there but room to add it, weird. 

That’s a very interesting bike you’ve got as the VIN # stamp on the frame falls outside of the VIN range of a ‘70 RT1 (black tank with yellow stripe) yet it also falls just outside the range for a  ‘71 RT1 with the close ratio transmission.  Possibly started its life as a non U.S. market bike ?? Combined with the fact that that you have a title for it further compounds the mystery.  I like a good mystery… my ‘70 RT1 has a similar mysterious lineage.  

Here's a different screen shot of vins. I read it as numbers above  >  52226 are still 1970 RT-1's all the way to the beginning of the RT-1B  ...then the RT-1B starts at vin 73101. So RT-1 72149 falls into the ">" above symbol range, but below it being a RT-1B. Where are RT1 vins numbered 52227 to 73101? Someone will know. Just the prefix RT-1 on the engine case without a number could be a warranty engine change but who knows. It would be easy to add the rest of the vin if it bothers anyone.
Need a RT-1 detective.

Could be a replacement case but the lack of stamped engine number and the "out of range" VIN points strongly to a JDM (Japanese Domestic Market) model that might have been brought home by a US Serviceman.

JDM bikes did not have engine VIN stamped fully.  In Japan, engine number was not required. 

I enjoy a good mystery!

The second owner was 87 years old,he had a storage locker full of bikes. Said he had a 1927 Harley but I didn’t see it. He had this enduro since 1974, last plated in 1984. Could have come in via the Naval Air Station in Fallon if it is a JDM. Added some new bars getting rid of the ugly.  

It's hard to tell in the pictures you posted but is the seat longer than normal for a US model? 

In my understanding, Japan also had laws about passenger seating and the JDM models sometimes came with a longer seat than the US model.  You'd also expect to find provisions (threaded holes?) to attach a passenger "grab strap" underneath the seat as that was a requirement in Japan and not the US.

Of course as old as these bikes are parts could have been swapped out over the years as oil tank obviously was.