GB Victorian Perfin - Can You Help?

I recently came across these two GB SG71 ½d vermilions, which were obviously a separated pair.

They are perfinned with the word "INVENTION" in an arc similar to the perforated Specimens. 

Can anyone assist with identification of this perfin? Was it a test (if so, they were postally used), or was there a business with this unusual name?

The GB Perfin Society website hasn't shed any light on this one, so any help would be greatly appreciated!