oldest tube(s) in your system

Yea, I figure 45 or 2A3 or similar would be about the oldest tube type still heating listening spaces.  Funny that as those are power tubes; would've thought signal tubes would be more likely to be oldest still in use.  All of our power tubes are new production babies.  And all of our signal tubes are older than me!

A pair of 45's in the Will Vincent Audio West SET45 amp. Along with a pair of 6C6 pentodes as input/driver tubes. Rectifier is a 5V4. The amp is built on a white powder-coated Dynaco ST70 chassis.

National Union 45's from the 1940's in my Supratek SET / 6SN7 preamp. 

I have no idea how old are the tubes in my system.  The amp and line stage run Western Electric 348, 349 and 310a, 310b tubes which were around from the 1940's through the early 1960's.  The 348's and 349's are extremely rare.  

Most of my 6sn7's and VT231's are from the 40's and 50's. National Union, Ken Rad, Sylvania, RCA, Raytheon, Tung Sol and no doubt others. Lots of nice vintage tubes, a few newer ones from Amperex and Electro Harmonix but mostly favor the ones from the 40's and 50's. 

I also have a group of 7n7's which I haven't even tried yet. I think they are 40's and 50's, all are metal base tubes. 

For 12AX and !2AU7, I mostly prefer tubes from the 50's, Sylvania GB Gold Pin 5751's and also Amperex Bugle Boys. 50's and 60's I guess?