On the first builds I made to test the lensfun branch, I used the “obsolete” MSYS2 lensfun". It is tagged 0.3.2
Then in the process of testing, I built myself the lensfun master branch(incompatible with preceding) which appears also as 0.3.2 in RT
The DB timestamp permits to know what is the more recent DB.
Effectively in the MSYS2 lensfun DB the name was
Tamron SP 70-300mm f/4-5.6 Di VC USD
While now in the more recent DB it is
Tamron Tamron SP 70-300mm f/4.0-5.6 Di VC USD
@Morgan_Hardwood: this lens is described in the SLR-tamron.xml file. regarding on which listed camera it is mounted, a crop factor is applied.