Do anyone know when Christmas lights started to have the green plug with fuses and the extra outlet for another string? Since I have a small Christmas tree from 1995 and I noticed it has a fused plug but the fuses aren't replaceable. We also have a star tree topper that I think is from 1992 but I'll have to look at the plug and see if it has a replaceable fuse.

Although, most of the newer light sets we had bought have the replaceable fuses.

We don't have any light sets older than 1995 anymore, but we used to have some from I'd guess the 1980s, that had the flower shade around the bulb. I don't remember what the plug looked like though.

I did see on this site, it said the non-replaceable fused plugs are 1977-1990, but like I said my set from 1995 has this plug on it.

http://yulelights.com/howo/set_ident.htm

Yeah, the fusible link (non-replaceable fuses) plug ran much longer than 1990. I still saw those on cheaper sets well into the 2000s.

My parents were married in 1976 and had no lights the first Christmas. The following year they did and I presume they purchased them new. They had the prong/receptacle combination with a non-replaceable fuse. They might have appeared a few years prior to 1977.

In my part of Canada, replaceable fuses are only starting to appear in the last few years.

those fused plugs on Xmas late 1970s into late 2000
had non replaceable fuses.  replaceable  fuses appears
in the late 80s on new expensive sets. then became standard on all sets.

fused plug came out when bulbs starting to have shunts
and it can happen all lamps EOLed and shunt all lamps
and heat up the wires to cause fires.  that  when all xmas set have fused.  now some of portable fans
are fused as well and use those style of fuses
it going to come to a point that all aplences less than 12 amps to have fuses.  cause they want to use smaller cables to save cost. 

Thanks for the info guys. Also I was thinking we have a plastic blowmold candle and it has a fused plug also, but the bigger kind like you see on electric candles or fans, etc. But we also have a blowmold toy soldier and it's newer than the candle but it doesn't have a fused plug oddly.

I have seen some old Christmas light sets probably from the 1920s, and they had a round plug with a receptacle on it as well, so those must have been around for a long time before fused plugs were added.

Also most of our light strings have an extra receptacle on the end of the string, and I'm not sure how long they did that. But our pattern or chaser lights don't have a receptacle probably since it wouldn't get constant power due to the controller.

Light sets with a receptacle on the end have two hots in parallel and one neutral. One of the hot wires has the lamps and the other one supplies power to the receptacle.