Half life is about 74 days. Ir-192 sourses usually start out at 100R. More information.
Correct unit would be R/hr.
This common radiography source travels from a shielded storage “container” via a crank and screw mechanism through a tube to expose a weld or other metal for inspection via image on developed film or more modern digital media.
Size of the source is small as described to travel through the tube of hte radiography camera. Because of its size, it behaves like a “point source”, i.e. dose rates fall off significantly with the square of the increasing distance.
A 100 R/hr dose rate at 1 cm from source would be <100 mR/hr at 1 meter distance and on the order of 10 mR/hr at 3 meters. Something to worry about if it was in your pocket or imbedded in you after a dirty bomb explosion but not a big deal if it was unshielded across the room from you for a while.
Commenters Right on the half life considerations, terrorists would have to move relatively fast or there is nothing but a non-radioactive BB left.