They could be from anytime in the late 80's to early 90's. Older if they have foam wrap grill... newer if they have cloth wraped grill.
They are nice little buggers... not the level of refinement you will find in the current TSM-MXe, but a nice two.way. Reasonable bass, good dynamics and the dissapeared pretty well.
If you have a pair of these, you may get a kick out of this page from a old Audio Advisor catalogue I had lying around!
http://www.sigsound.com/images/Merlin1B.jpg