One of my favorite Manley popcorn machines is the Model 47 (M-47).
It is similar to the M-46, M-48, and M-49. In this case, the model
number refers to the year of manufacture. Starting in 1952, model
numbers referred to the model, not the year of manufacture. Prior to
1946 no model numbers were used, however they did sometimes use lot numbers.
There is some confusion on the model numbers of the Manley popcorn machines.
For example, the model number listed on the following machine's ID tag is
47, not M-47. The Premier line also used model 48 and model 49, as
well as a model 50. The Aristocrat was introduced in 1950. An M-50 has
not been found. So, if someone mentions a model 48, it could be either
a Premier or M-Line model.
Below is a photo of my restored Manley M-47. You can see the
restoration process at my
Manley Model 47
Web Site.

M-46 through M-49 Restoration Page This page contains information on
restoring these Manley popcorn machine models, including suggested
replacement parts and a wiring diagram.
Manley made a counter top model as well:

Manley also made a larger version that was two machine in one for places
that needed large amounts of popcorn:

The Manley M-47 appears to be identical to Patent 2,536,298 granted to
Charles T. Manley, deceased and assigned to Manley Inc. The patent was
filed on April 10, 1948 and granted on January 2, 1951. You can search
for patents at the U.S. Patents and Trademarks Office at
http://www.uspto.gov/patft/.
According to an advertisement in the November 15, 1947 Boxoffice
Magazine, "all of the metal paneling and work surfaces are made of silvery,
good-looking Monel." Here is a link that describes Monel,
http://www.lenntech.com/Monel.htm. According to this web site,
stainless steel began to replace Monel in the 1950s.
A scan of the Manley M-46, M-47, M-48 instruction manual in pdf format
follows:
Instruction Manual