Not many of these sold, even fewer left.

The bike was first registered in August 1973.

Rear light will, I think, be unique to the UK, the seat won't be the same as US, lights on/off is on the left switchgear and note the blue high beam lens.

I'm tempted, but looks like a lot of work!

Yamaha DT175 (CT3) 1973 Classic Motorcycle | eBay

You're right there--looks like a lot of work. Exhaust appendage looks same as one model of AG175 we had in NZ but our AG's had it side-on so it spat oil over the tire. Not sure about 21 wheel on the front as 18 was std & 19 on our AG's. Seat looks bloated like it's been re-upholstered with a bit of padding added. Tacho is off something else yamaha. Maybe i'm just getting picky in old age. If it's rare & ya want it--well--there it is.
Here's a random pic off the net which shows exhaust extension. 

Seat is probably correct - Euro, like Japan, got the twin seat + strap. Likewise the tacho is correct, just the way the photos are taken.

just think of how fun it will be to refurbish that little gem and how fun it will be to ride it around too!
you only live once!