Ah yes, the adjusters threw me too. But, here's what I found, which I think proves these are Universals:

1) I swapped an adjuster from a model 68 with the "mystery" lever, same threads
2)I found my old mostly trashed Universal 68 hoods, they fit the "mystery" lever just fine
3)check out this website, they mention the model 51's and earlier Universal levers having knurled adjusters, and also there's a pic at the bottom of one w/ white hoods, looks just like these ones
http://www.classiclightweights.co.uk/universal.html

Whatcha think?

mark