Specto 1,5 inch/f1,9 Projector lens

I found this little lens on an antique store. It's body remind me of my Dalmeyer 1,5 inch.
I never know this "Specto" brand before. So I just bought it.
Then searching in google...found this site quote from that site

The lens, captured with Meopta 701,4

The machine was supplied with a 1.5 inch (35mm) focal length Dallmeyer lens of around f1.9 aperture in a 25mm mount...

 tadaa..it's Dallmeyer in disguise.I found on ebay seller who selling Specto projector, he said his item fitted with taylor Hobson 1,5 inch/f1,9 lens. Could it be TTH lens? I doubt about it. As TTH 16mm lens has smaller coverage. even 2 inch supertal TTH has strong vignette on mirrorless APSC cam.The results are similar to Dalmeyer 1,5 which is very unique. Here it is...4 images shot with NEX5

And  with EPM1 below

This one was shot with dalmeyer 1,5", see how similar to Specto

Dallmeyer 1,5 inch projection lens

Almost all lenses have something written on it description of focal length (eg. 50mm or 2inch) and it's capability to let light through (eg. F1,4). Projection lens also has this. But not this Dallmeyer lens.

 I saw other Dallmeyer projection lens, only has marked 2,5 inch. This one has 1,5 inch which is approx. 37,5mm. 

I use it on Sony NEX5, slight fall off on corner in certain objects.