Uhm, it was introduced and clearly qualifies as universal directional dynamic studio grade microphone and can be used for almost any near-field duty on voices and instruments (sans kick drum and cymbals, maybe) and has nice features, hum cancelling for example.
For a long time, it also was the go-to mic for reporters and live broadcast. This mic was very present for many decades in Germany and in my personal life.
There also was a Star-Trek style table stand:
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en.wikipedia.org
Hmmm... Been too many years so I can't argue with that. I remember using it as an instrument mic, and am pretty sure that's how Sennheiser listed it at the time, but I don't have one now, and did not look it up on the Sennheiser site. The only thing I remember is that, while it did a good job handling high SPL (150 dB+), it rolled off around 30 Hz (as did/do many "instrument" mics). The 600-series had higher LF roll-off (may have changed since then, been a while). I used the 421 and a 902 (? -- side-fire, went down to 20 Hz) on the drums and guitar cabs, but most of my mics were Shure and AKG models so I may be misremembering (senility).
I remember the little stand -- I put it on the floor in front of the kick drum, or under the toms (which provided some "interesting" effects but ultimately I did not care for the "boom").
At this point I don't have any but the strongest of memories from that time, if even those, so am probably wrong. Oh well. My memory is one of the studio recording engineers said to get those two dynamics for drums and bass guitars as they were relatively inexpensive (not to me at the time!) and much more robust for stage work. Except for the drums, and sometimes acoustic guitars, pretty much everything else on stage used venerable (if peaky) Shure 57 or 58 mics. The condensers only generally came out when I was recording a group of vocalists or musicians like a quartet or chamber group, or for a symphony, not a rock or country band. I learned the hard way that condensers react poorly to drops from stage to floor...