The TX750 in your photo has a separate pipe system, and as far as I know that was what was fitted to the handful produced, no options.
The TX was not a 'production racer', a real Production Racer (Norvil Commando) by definition had seperate pipes with peashooters.
Norton factory F750s also used separate pipes.
Many racers using Seeley frames and ridden by UK national and club racers were fitted with 2 into 1s of varying designs and quality, and some may have been ridden in F750, most weren't.
So what have you really been offered? a 40 year old 2 into 1 race system built for a Commando? or a Seeley? Unless it is pristine and you want to hang it on your wall, it probably has no real value at all.
If you are building a race bike it is definitely of no value today and you would be better off getting the likes of NRP to fabricate something that will meet noise regs, at most the down pipes might be usable if not corroded.
If it is for a road bike, same problem.