Info added to the sale: Crystal made by TEW denpa co. ltd (Tokyo, japan), outer shell made of glass.
Interesting! Where did you come by this information? I wonder if we can find out more, like the ppm specification.
In the same crystal: Y1: 1351544 4.00MHz TEW5 43 A
TEW appeared after looking it up was as prominent company specializing in crystal oscillators from way back, as of today, hence the link.
The first number must be the model or manufacturer ID of some sort, but its not currently listed anywhere. I sent a inquiry to them to see if the could get me some more info and I'm waiting for the answer.
The outer glass shell is because at the time it was used, but I must confirm it still.
I recommend this series of videos to anyone wanting to get a quick review of crystal oscillators. He shows some vintage ones:
Finally, to sum up my sentiment:
When the rain came I thought you'd leave
Cause I knew how much you loved the Crystal
But you chose to stay, stay and keep me warm
Through the darkest nights Ive ever known
If the mandolin wind couldnt change a thing
Then I know I love ya
Oh the rubber domes fell without a break
Model M died in the frozen fields you know
Through the coldest winter in almost twenty five years
I couldnt believe you kept your shine
Now I can rest assured knowing that weve seen the worst
And I know I love ya
Oh I never was good with romantic words
So the next few lines come really hard
Don't have much but what Ive got is yours
Except of course my crystal
Ha, cause I know you don't play canned
But I'll teach you one day
Because I love ya
I recall the night we knelt and prayed
Noticing your caps were thin and pale
I found it hard to hide my tears
I felt ashamed I felt I'd let you down
No mandolin wind couldnt change a thing
Couldnt change a thing no, no
The coldest winter in almost fourteen years
Could never, never change your mind
And I love yer 4 Mhz
Yes indeed and I love your trans-lu-cen-cy
And I love yer Quartz
Lordy I love ya Crystal