Introduced in 1915 the Neptune rowboat motor was Caille's inexpensive motor...it was not the later badge motor.
It was available with either battery or magneto ignition.

Caille Neptune was a straight blade prop (non shifting) version of the Caille Rowboat Motor. The "standard" Caille RBM was a 5-speed. 

As the Caille ads said, "A dandy, low-priced motor for general use.".

There was also a canoe version, and a 3 1/2 hp commercial version which I have never seen.

They always had a dry exhaust.

Neptunes were sold
unpolished
as an economy move.

So if you have one
don't polish it!!!

Neptune

1915 Neptune

Great company letter concerning Neptunes.
This clearly documents the differences between the
Neptune line and Caille line on page two.

GREAT BROCHURE!

Design of tank: As far as Jack and AOMCI Caille specialist, Randy K., have observed, it changes over time. That embossed tank was used on both the Caille Neptune and the 5-Speed Rowboat Motors. Plus, some of the very early embossed tanks did not have the brass “bars” on them. 

As Randy recently wrote, "I’m quite sure they were all painted as this one has been. For the most part, until about 1925-26 they were all painted this green color, after that it seemed as though some were also black or a very dark red. As Jack would say, this could all be debated as the paint darkened or at least has changed color since new, so it’s just an educated guess."

NOTE: Much later Caille manufactured a Neptune Twin for Montgomery Ward.

Jack wrote, "I did not know this until I bought a twin in the original box. The crate gave evidence of the connection and I tracked down an original 1926 Montgomery Ward catalog which advertised the Neptune Twin.
I do not know when Montgomery Ward started handling the Neptune, but Caille did not make the Twin before 1925."