I had also thought that it might be a house brand, but it appears not.
Pro Arte is an English brush manufacturer.
Here is their website
As I said, I have used the Prolene Plus rounds. They are a synthetic and are wonderful brushes.
Now I'd like to try the Connoissuer rounds - they are a synthetic/sable mix.
Pro Arte brushes are sold all over England and perhaps all over Europe, but I have not seen them at any of the U.S. online retailers except Jerrys/ASW which I realize are the same company. Perhaps Jerrys/ASW has a U.S. exclusive?
Thanks for checking into it.... they really are great brushes....
Similar to the Da Vinci Cosmotop Spin brushes that I have purchased from you and which I also love !!