The crystals for the Paraset is of the big size. They fit direct in a power outlet!! I used the cabinets and placed smaller crystals inside.
The first crystal controlled transmitter was in a university in USA in 1924 on 3 Mc and about 5W. Not long time thereafter hams started to make their own crystals.
The army didn't use any crystals. They used the freerunning VFO. Under the WWII it was impossible to get 4 different rigs (2 RX. + 2 TX) to spot the same frequency in same time. They needed crystals...USA started the big productions. At the end of the war, about 30.000.000 crystals were made per year.
From Brazil, the only big mines in the world, the industries started up. USA buyed all quartz they could get.
The crystals was grinded to right frequency from the beginning. This gave ageing problems, The frequency was rising after a while. The more expency methode, etching, was later used.
In 1932 it was an article about crystals in the QST what changed the situation for many hams. In 1935 the new tube 6L6, and later the 807 came on the market. 6L6 was too strong for many applications so the 6V6 was developed. These tubes were the grounds for many amateurs after the war, and a big surplus of cheap crystals.
Big crystals, easy to handle.
A big porcelain housed crystal.
Modified with a small modern crystal.
Link to Bliley Crystal history