Monnin Watch Cases

What Are Monnin Style Watch Cases?

What collectors call the “Monnin case” is a unique style of dive watch case. It has a distinct look with a flat, rounded shape, lugs that are wide but not too sharp, and a crown guard that flares out and hugs the crown of the watch. It manages to be both practical and stylish and is seen with automatic movements as well as quartz movements inside. When you wear a watch with this case, it sits comfortably on your wrist because it’s relatively flat. However, if the watch has an automatic movement, it might need to have a slightly thicker case back.


Over the years more than 100 different watch brands have used this special case design for their watches. These brands range from A to Z, including names like Adura, Aeritalia, Airin, Aquadive, Zenith, Zeno, Zentra, and Zodiac. But perhaps one of the most famous brands to use this case is Heuer. They used it for their well-known 844 and 8440 dive watches, which they introduced in 1978 that essentially save the company from being another victim of the quartz crisis.

The Birth of Monnin Style Watch Cases

The Heuer Reference 844 is known as Heuer’s first dive watch and holds a significant place in the brand’s history. Even though Heuer was well-known in the racing world with their chronograph watches, the “quartz crisis” in the mid-70s caused financial problems for the company. During this period of time, new watches powered by batteries appeared. They had two big advantages over Heuer’s traditional mechanical watches: they were more precise in telling time and they were less expensive.

However, the introduction of the 844 changed the game for Heuer. This dive watch became incredibly successful, and many people believe it rescued Heuer from the financial struggles almost all watch companies faced.

Heuer Reference 844

At first, Huer had all the assembly done by an outside company called Georges Monnin, which specialized in producing dive watches for various brands, including its own. However as the 844 became more and more popular Heuer moved the production from Georges Monnin’s facilities in France to their own factories in Switzerland.

Monnin, who is still around today was essentially a watch assembler and not a case manufacture. The actual cases were made by The MRP SA, a Swiss case manufacturer which held the Swiss patent CH503305A for the design of the ratcheted, unidirectional rotating bezel.  MRP SA – which also still exists today – supplied these cases to Monnin as well as many other companies assembling watches.

MRP SA Swiss patent CH503305A

During the time Monnin was assembling the watches for Heuer, the inside of the case back was marked with both their name of C. Monnin, MRP SA, the case manufacture, along with Brevet, French for patent and the Patent # 503.305. 

It was the fact that Monnin had their name engraved inside the case back that started the association of the case design being known as a Monnin case.

Heuer 844 with case back

Early Heuer 844 Case back

The Influence of Collectors

Watch collectors have played a pivotal role in preserving the legacy of Monnin style watch cases. Vintage dive watches with these cases have become highly sought after in the collector’s market, driving up their historical and monetary value. Unfortunately there are people trying to sell watches for Heuer 844 prices using the Monnin name.

As I mentioned earlier, MRP SA made the same case for other manufactures. Here is an example of the Aquadive with a “Monnin” style case. Notice the absence of Monnin name from the case back. Clearly made by MRP SA. I have seen this watch listed with the patent # used as the reference number for the watch as well listings saying the case was made by Monnin trying to boost the value of the watch.


Aquadive case back

You will also see watch cases listed as a “Monnin” case that no longer even feature the MRP SA name inside the case back.  Only the Patent number is listed. This is due to the fact that the patent ran out in 1988 so anyone could make a case with the same style bezel at this point.

These watches have no significance in watch collecting so you would not want to pay premium prices for them.