You have the choice.
I think it is preferable to have a good weight to evitate vibrations.
maybe these: - Standard Goliath vise
- Standard DoveTail but the jaws height for me are to small.
http://airgraver.com/4140_Series_Engraving_Blocks.htm
or if you have money the Large Glide-lock Vise ;-)
http://airgraver.com/Glide-Lock-engraving-blocks.htm
PS: Don't forget if you want to work with binocular to order a turn table ;-) (not with Glide lock vise)
http://airgraver.com/hand_engraving_vises.htm