Bach train set- N - P/N 900 70C How old is it?

[KoalaTrain]

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I just received a train set from a relative.  They say it is old- possibly the 1940's or 1950's, but I can't find any information at all about it !
HELP !!!! PLEASE !!!!

It says Bach on the box  P/N 900 70C    It is "N" size

There is an engine, 2 cars, a caboose, and 10-12 pieces of track. It also says American Freight Express on the box, but this may have been the shipping company (or maybe the name of the train set)?

I don't know anything about trains.  I don't know whether to keep it or sell it either!

Thanks for any information.......   

[the Bach-man]

Dear Koala,
We made our first N Scale sets in the late 60's, so that will be your age limit. As for value, the old sets don't have much...
Happy Holidays!
the Bach-man