Updating my own post once again with a new ad from the same online group devoted to vintage ads.
This one is a little disturbing. I'm not too appreciative that Lionel was trying to get kids to be this conniving. Given the catalog images, I'm going to place this from in the mid- to late-1960s.
The best comments from viewers of the thread had the father pause to reconsider his words:
...But, for gosh sakes, DON'T tell Mom this is the most fun i've had in years!
and
...Well, the most fun since that weekend last year with Cindy from accounting!
Enjoy.
Steven J. Serenska