That's the original 185 series Odoriko (おどり子号).
Here it is in the 1997 version of the Plarail Encyclopedia. It says that it was released in 1983 and production stopped in 1990.

According to the 'Plarail Museum' those are both '6th Generation' boxes, which were used approximately 1987-1994.
This is the cover of the May 1983 catalogue, note the logo top right:

...and sure enough, there it is for the first time, fifth down on the left.
