Vintage Dallmeyer Lens, please help

Hi, I'm reaching out to several people hoping to get some information on a lens I found. I was able to find the maker but not the exact lens. Any help you can provide for information and where I could find a value would really be appreciated. It's a dallmeyer London f/1.5 f=1 1/2 no.125432. I can be reached directly at lilysmom826@yahoo.com