metadata - How to add EXIF Lens data in Lightroom for unknown lens?

One of my prime lenses is non-electronic and so the photos EXIF data does not include any lens information. These show up in Lightroom 4.3 as "Unknown".

I see no way through Lightroom to add this lens name, focal length, etc. The photos are spread across folders, so doing it manually with an EXIF like this one will not work https://exiftool.org/

Does anyone know if this is possible?

Thanks.

Answer

Well, if you have good scripting skills, EXIFTool can be made to do this across folders. However, there is a donation-ware plug-in for Lightroom called LensTagger that may do the trick for you.