Currently working on an Ossa  MAR basket case & TR77 basket case (punishment I know) but not sure if this exhaust is off either....Can anyone help identify please?

The middle part looks the same as my own MAR,

  the silencer - I cant remember ever seeing one like that on an Ossa

the front pipe could be TR77  { they are that shape - MAR is much shorter }

 

That's a TR77 exhaust complete

 

Thanks Woody?. My first post & definitely not going to be my last, I'm sure. 

Yes a tr77, but on my old one, the tail pipe wasn't welded to the rest, there was a gasket and a twin Spring connection that connected them by pulling both parts together. I'm not sure whether the 250 and the 350 had differing connection methods!