Sounds like a Dynafile. Quite common in machine shops. Very fine work can
be done with them with a bit of practice. Common tool in the debur room
where one slip can cost thousands.

"Prometheus" wrote in message
...
I used an air version of a similar tool- it wasn't a grinder
conversion, but a standalone thin belt sander with a handheld grip.
The idea is neat, but I found that for myself, it wasn't all it was
cracked up to be- the two major problems were that the belt liked to
slip off the roller on the end no matter how it was adjusted, and was
a PITA to put back on, and because the belt was so narrow and moved so
quickly, it had a tendancy to gouge things very quickly.

Useful for rough work, an maybe carving- but not really a finishing
tool in any sense of the word.