This crystal is one of the best crystal's I have ever owned. I dare to say that it is still at 100% output, and I have owned and played through enough MC-151 crystals to know when one is fantastic, just good or just OK, weak and of course dead as many vintage crystal mic's are these days.
Anyone who has a low watt tube amp for harp, have a look at the RCA speaker in my other listings. This is a rare 12" extended range speaker that is rated at 95db at 1 watt. Extremely efficient and the sound is just phenominal. Freq range from 50 to 16kHz!! I tried it in my Blues Jr. and it sounds incredible, better than any other speaker that I've heard including the Pro Series Jensen P12R that I absolutely love in my blues jr., but 15 watts is a bit too much for it. It's rated at 10 watts and it is expensive, but I guarantee that it will be louder and sound better than any other speaker you've had with your low watt amp! Have a look!