1939 IOM TT...just how heavy were the racing motorcycles?

Ever wondered just how heavy IOM TT racers were? Ironically when you present for scrutineering prewar, they called it the "weigh-in" and they actually weighed the motorcycles.
Unsure if they still do it for todays GP racers, but they were doing it some little time back, as there was a minimum weight for each of the racing classes.
1939 seems to be the last and perhaps only time the motorcycling press ran a page on it..."MotorCycling" did it and published it in their June 28 1939 edition, page 319.
From a Velocette point of view the weights of the Veloce Ltd factory machines, as ridden by Stanley Woods and Ted Mellors were heavier than the standard over the counter production racer KTTs.
I've included below pages from the TT program of that year with notations where I can identify them of whether the Velocettes were Mk.7 or Mk.8 KTT. The Mk.7 has a rigid frame and is lighter than the Mk.8 which has a swinging arm frame the same as the factory racers.
The engines in the works Velocettes had larger cylinder head fins and a bigger cylinder barrel.
The Mk.7 and 8 KTT had a 9" square head with the factory 10" square, so more aluminium.
Interestingly the factory racers often had an aluminium petrol tank but the gearbox final drive sprocket was solid steel and had no holes drilled in it.
Plenty to ponder there....
I've include a photo or two of relevant Velocettes both standard KTT and factory machines and a works BMW which was the lightest bike in the Senior race!
Acknowledgement is made to Morton's Motorcycle Media for the "Motorcycling" page, the authors of "Always in The Picture" ,the Late Bob Burgess and Jeff Clew for a photo and S.R.Keig and Fox Photos for other photos and the ACU of GB for the IOM TT program pages.
First photo is actually a 1937 works 500, but they were the same. Illustrated is Ted Mellors bike.
Second photo shows a mk.8 KTT, well a brace of them in the race shop in May 1939.
The third is a mk.7 KTT in the paddock in June 1938.
Final photo is reputedly Schorsh Meier's machine, but could be Jock Wests...pic taken by me at the German BMW dealers shop in Munchen, April 1974.
Left click on photos to enlarge.....