I don't feel the urge to apolgise: I have no first hand knowledge of SD Triumphs so I doubt I'm the person to ask. Anyway, since you sound pretty desperate, let me have a go.
Assuming the bars are the originals from your bike, let's assume it is used for something. Does your bike have a stirrup front brake? Maybe something to do with that? If the bike has two inverted levers (front brake on the right, exhaust lifter on the left?), these cables must come out of the inside of the bars somewhere. Is is obvious where this happens? Maybe the exhaust lifter comes out somewhere along the left bar, but the brake cable comes out directly above the stirrup brake, in which case the thread might be for a spring box (for the return) and where the cable joins to the brake rod.
Possible? If not, does it mount one of those single-stem Lucas electric headlights? (Does the bike have electric lights?)
Do you have a parts list? Sales brochures? Magazine reports? Adverts? Photographed every detail of every SD and Ricardo you've come across? Research should really come before nickel plate.
Cheers
Leon