I just bought a used centurion amp. I looks like it's new. The serial number is 05A10074. Can anyone tell me when it was manufactured? Dave N1IX Fists #1569 Geratol #1994 QRPARCI #8475 NAQCC #1130 SOC #26 NEQRP #331 FP #393 SKCC #2255 K2 #5281