Sennheiser 421 time-line

[Silverjet89]

So I just got my first 421 off of craigslist. Its a white MD421-N with only one bass roll off position and proprietary cable. I know it's an old version but was wondering if anyone knew the years that this model might have been produced.
I did a web search and found descriptions of the different models but nothing that really narrowed down the years of production.

The thing sounds great so it doesn't really matter how old it is. I'm just curious.

Thanks,
Kirk