It's quite possible those tube are not the originals. Someone could have "shotgunned" all the tubes tracking down a problem. Since many repair places buy their tubes in bulk, they'd probably have all those tubes on hand and they all just happened to fall into those two date codes. 
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Pioneer SX-1080, Pioneer PL-115D, Pioneer CT-F9191, Pioneer RG-1, Wollensak 8050A, Akai 4000DS MkII, Pioneer CS-05 & Polk 1.2TL
Denon 5803A, Pioneer DVL-700, Pioneer CT-W603RS, Toshiba HD-A3, D-Link DSM-520, Dish VIP-722, Polk 1.2TL, CSi5, LS/fx, RT-800 and PSW-650
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