Glass Envelope Quartz Crystals

Here are pictures of some interesting glass envelope crystals I received today in the mail. I'm not sure if I should call them "vintage"; they aren't that old based on the date stamps. Very interesting nonetheless. I hope to use them in a project in the future.

5 MHz Glass Envelope Crystal

Better view of the mount in the 5 MHz crystal

Bottom view of the 5 MHz crystal

25 MHz glass envelope crystal

Back side of the 25 MHz crystal

Bonus: 10 MHz PK-171 crystals

- Dan W.