In the early 80s, when all SLR are manual focus, Tamron launched a range of lenses, with separate lens mounts (the Adaptall2), the user need to buy a separate lens mount, eg if u use Nikon buy Nikon mount, if later u change to Canon u keep the lens and just buy a Canon mount, etc.
Now, if u have a old Tamron lens, u must also need a Adaptall2 mount, there should be marking on the mount to say what brand it is for.