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MFY Tungsol 6550 tube old versions

In my ARC REF 3 I 'm using a Tungsol 6550 tube with the following code written on the metal base 322NU 3 , it is a smooth grey plate , without holes in the plate .I know 322 is the factorycode of Tungsol and normally the 322 is followed by eq 63=year 45=week 3= shift ?.But I have seen also 322HN-3 and RM-3 .Is there any list of these codes ?
Any help would be wonderfull
128x128hansk46
jedinite24's avatar
jedinite24
1,503 posts
 
Have you tried contacting Brent Jessee or Jim McShane? Those are to NOS tube experts. They should be able to help you.
xti16
1,525 posts
 
Oddlots - I had some smooth grey plates with letters in place of the year. I got them from Brent Jessee but traded them a while back.
hansk46's avatar
hansk46 OP
122 posts
 
At first thank you Jedinite24 for JimMcShane 's address ,I sent him an Email , even to tubemuseum and newsensor , just have to wait , and yes Oddlots , I 'm sure it is a smooth grey plate without holes , and looking at the foto 's and description of Tubeworld it could be from 1960 to 1963 , but still want to know the meaning of the code
xti16
1,525 posts
 
Hansk46
If you do get a cross reference list could you please share it.
oddlots
13 posts
 
I'll email Brent Jesse about this as well and let you know.
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