This sounds like an unusual light string - do you have any pictures showing how both the receptacle and the Tachon connector are connected to the string? It seems odd it would have both. I can't be of much help dating the string, but it would be interesting to see a picture of it.
In going through some things the other day, I came across this plug and receptacle. The receptacle is marked NOMA on the backside and I wonder if this looks similar to the one connected to the end of your light string?