Stepper motor questions

I recently purchased a few of these steppers:

http://www.brigarelectronics.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=BE&Product_Code=100SR

The steppers have no labelling at all on them. From the gummy spot, a
small label seems to have been removed from all of them. The coils are
3 ohms each (with ohmmeter lead resistance subtracted). Although the
claim is made in the ad that they require 6 amps, they are quite small
(the cube part of the body measures 1.53 x 1.53 x 1.24 inches), and
when I run these over about 2 amps, they start to overheat. The face
of the mounting 'diamond' is machined very flat, so heat sinking
appears to be intended in the design, I guess.

Does anyone know what current these are designed for? Or the actual
specs on them?

TIA,
Grant