Older Sennheiser MKH models

I can't help you directly, but if you don't find an answer here you could try Sound on Sound forum [hope it's legal to mention other forums here].

There's a fellow used to post there frequently by the name of John Willett who is a Sennheiser rep and has just about all spec and history at his fingertips. He might still drop by occasionally. A very knowledgable guy.

I found the post on SOS regarding older MKH mics. Ends up it was a question asked to John Willet by Gunnar Ghellquist regarding a pair of MKH 406's aqcuired by Gunnar [frequently part of this forum].

The post is
http://www.soundonsound.com/forum/showflat.php?Cat=&Board=MRT&Number=9911&Searchpage=2&Main=9911&Words=MKH+104&topic=&Search=true#Post9911

Hi,
just chiming in very quickly (on the run).

I found a pair of MKH406-s on the net. They are with me at every gig, and I really like them. I believe they were designed with an 80Hz high-pass filter, which generally is a good thing, but not always. Otherwise they sound very much like later MKH-s -- boring is one word I have sometimes thought. In a good sense that is, not adding anything, just catching what it sounds like. For on location recording that is perfect if you ask me.

Gunnar