Hello everyone!

I'm new to this forum, and I have a question I hope can get answered...

I was helping my grandparents clean out their attic, and I found my old train set, in perfect condition!

I took it home to my house today, and upon examination, I cannot locate a manufacturing year.  I was wondering what I should be looking for in order to obtain an accurate date for these pieces.

The set I have is the Big Smokey HO Electric Train Set, and comes with engine and kaboose, several cars, track, power pack, bridge, water tower...and some plasticville items.

I was born in 1976, and I remember this train set from when I was really little, so it must date around there somewhere. 

Any help would be much appreciated!  Thanks in advance!