Gravely made both circular saw and chainsaw attachments.
The chainsaw used a chain size that hasn't been manufactured for at least 30 years. The circular saw attachment was basically a 30 mower with a saw blade rather than a mower blade. The early models didn't have any guard. Later models had a guard that looked like a cut off 30" mower deck.
Both look scary as heck to use. I think that both were made for cutting trees---not brush.