Merry Musical Makers!
These little guys not only dispense candy, but they play a tune too. It's probably the most awful tune one could imagine, but they are whistles. The only one that lives up to its name is the Duck MMM. It truly sounds like a duck call, by a very sick duck.

Let's start with...ummm...Lamb.

It's a common myth that MMM's were never sold in the United States. Wrong answer. This would be incorrect as Lamb MMM was sold here in the good old US of A back in the 70's, as were Duck, Pig and Rooster. All were non-footed (NF) back then, but were still being released in Europe when feet came about.
The variation to look for with them would be the head color. The ivory being the older and white the more recent issue. One can get a better look at this Variation by looking at the patriotic trio below...

The guy on the right has the ivory head. The patent numbers on these can be anything from a 2.6 to a 4.9. Here's a listing of some:
Ivory head, A, 3.9, NF, Pink.
Ivory head, A, 2.6, NF, 3, Blue.
Ivory head, A, 3.9, WF, 3, Pink.
White head, A, 2.6, NF, 3, Pink.
White head, A, 3.9, NF, 8, Red.
White head, Y, 3.9, WF, 5, Blue.
White head, Y, 3.9, NF, 5, White.
White head, Y, 4.9, WF, 5, Blue.
White head, J, 3.9, WF, 5, Blue.
And I'm sure there's many more!
Now for the Duck Call guy!

Not much to say about them. The stems can be footed or non-footed. Shown above are a 2.6 and 3.4 NF and a 3.9 WF with no spine. What's a no spine you ask? Continue on...
The Frog MMM will give me a chance to explain the no spine stem.

Almost all non-footed dispensers will have a small spine (ridge/seam) going up and down the back and the front of the stem. Almost all footed dispensers will have a raised back spine and a small spine in the front. What's unusual about this dispenser is that he is footed, but does not have a raised spine in back. Would you look at those two silly Frogs. Will one turn into a Prince? I don't know.
Here's something cool.

This is a close-up of the green stemmed Frog shown in the previous picture. See the pattern to his head? I like that kinda thing. But I'm also building a complete website on Pez dispensers, so that shows where I'm at. Also worth metioning is that the eyes of the Frog can be quite different. One will have clean stenciled eyes, and the other looks like it was painted by me in my sleep.
Pig

How about that red blower? Pretty nice looking, eh? (I did that for my Candian friends)
Here's another simple one...Camel.

These guys will always have painted eyes. Don't they look happy? Shown are green (Austria, 4.9), blue (no country marked, 3.9) and gray (Yugoslavia, 3.9) stems.
Speaking of happy, look at these guys...

These are the Indian MMM's. Sometimes you'll get a slight Variation in face color with these. Other than that, you'll have to look for some stem differences. Shown above (from left to right) are, again, a 3.9 no spine, 3.9 Yugoslavia, 3.9 no country marked (IMC 5, so it's Yugoslavia), 4.9 Slovenia and a 4.9 Hungary.
Here's another happy dude!

This is Clown. He's a bit too happy. Like Froggy, it's the eyes that set them apart. Some are stenciled and some are hand painted.
See?

Messy...clean.
As long as we're on simple, let's rip through a few more...

Nice face color Variations on these. One would think that maybe the dark color would be on the NF and the light would be on the WF, or vice-versa. Nope. No consistency here.
Tiger

He's sleek looking isn't he? Some cool stem colors to look for, but let me show you a cool stem on the red guy above.
Stenciled stems...

This is kind of a transition item. The stem is molded with a normal stem marking, 3,942,683 Made in Yugoslavia. But, they wanted to update it with the new patent number, 4,966,305. It also has Made in Yugoslavia stenciled on it again. A bit redundant if you ask me.
Look...

I wonder where this dispenser was made.
Rhino MMM

Another fun one to look for spineless! And the different color blowers are cool, too.
Simple? Yes. But...

Monkey may be simple, but the stems on these never cease to amaze me. The tangerine is just awesome! And I don't really care for tangerines.
How about Donkey?

One of these really stands out, huh? Yep, that brown stem one is cool. Oh, and the peach is quite unique too. The peach one is a test mold. What you may find with some test molds is that the kicker has been removed. It's been said that this is done by the company. Who knows. Here's a shot of the Donkey's rear...don't even go there.

See where the kicker was?
Koala

Once again a no spine, a couple footed (3.9 Yugoslavia and 4.9 Austria) and a handsome NF blue stem guy. Actually, now that I think of it, all the Animal MMM's can be found with the no spine stem.
Penguin

My camera is not the best, so you may not be able to see. But, the Penguin on the left is the dark, dark blue head variety. One thing you can see (my camera's not that bad) is the difference in the beaks. The dark, dark blue has a longer beak. See, what happens is, if one pushes on the blower, the beak sticks out farther. Short blower, long beak. Long blower, short beak. You're not buying this, are you? Good. Because I made that up.
Parrot

This is a nicely done dispenser. The yellow is quite unique. He is on a blue no spine 3.9 Austria stem. There's something about the look of him. He's just too pretty.
So pretty, I'm going to take another shot...

And a red blower to boot.
Rooster

This guy is very similar to the regular Rooster dispenser. Just stick a blower in him, change the face piece a bit, and walla! I like the inner sleeve colors on this guy.
Look at this...

No animals were hurt in the making of this site.
Panda

Like the Rooster above, the Panda is very similar to the regular dispenser. Shown above is Panda "A." He has removable eyes.
Here's a close-up...
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One the regular (non-MMM) Panda "A" dispenser, the eyes, ears and nose are all removable. On the Panda "A" MMM shown above just the eyes are removable.
Here's Panda "B"...

This guy has no removable parts. Boring...
And now for my favorite whistle of all time...

These are my favorite whistles. They are called Coaches Whistles. The ones shown above are the first series. They are all made in USA and have the 3.8 patent number. Since they were made in the United States of America, we know that they were made in 1978-79, as that's the only time dispensers were made here. The colors on these older ones are great. Somewhat pastelly. What do you mean that's not a word?
And here's the latest version of Coaches Whistles...

Now this may get a bit confusing, so bear with me. See the whistles in the front? Of course you can. The ones in front have a 4.9 patent and are made in China. Let's use the red, white and blue for our example. The small loop on it, where one would attach the string, is white. Now, the ones in back are 3.9, either Made in China or Made in Hong Kong. See the loop on the red, white and blue one in back? It's red. They reversed the mold. Now up until recently, I had always thought the loops were the same on the 4.9 China stems. Not true. A collector friend of mine informed me that the loop on the 4.9 China whistles can be found reversed. So get out there and look.
Here's a close-up of two.

These are both 4.9's.