Hello Schwartz04,
Gyro-Trac base machines were originally built based on the design of tracked carriers made by Bombardier. This is except for the GT-50 which was built based on the design of a tracked machine made by Plaisance Equipement, in France. See:
www.plaisance-equipement.fr/index.php/eng/accueil/machines_automotrices/galotrax
You could contact Plaisance Equipement directly to find out more about the Gyro-Trac GT-50 history. Their phone number in France is 0033 (0)3 83 42 15 79.
Their former cutting head technology with swinging tooth was based on the design of the head made by ROWMEC. You could contact John O'Hagan Sr. at ROWMEC to find out more about Gyro-Trac's original 500 and
700 cutter heads. Their phone number is 936-539-5488.
Now, Gyro-Trac build their "fixed-tooth planar heads" using DENIS CIMAF patented technology, although some of their ads might lead you to think it's their own invention. You may have a look at:
www.deniscimaf.com/en/products/technology/brushcutting-chipping-rotor.html
I know, we don't have much pictures there yet. We're working on that

But by going through the site, you'll find some image galleries where I think you should see some closeups of our rotor. You'll notice that our newer models have their teeth positioned in chevron, or inverted V's, while Gyro-Trac models have their teeth positioned in spiral.
As far as some Gyro-Trac operators who could give you their feedbacks, I might have a few people you could contact, but I'll get their permission first before posting their name here. And hopefully, some others will reply directly in this thread.
Best regards,
Frederic