Differences between Caliber 51010 and 51011

When I was planning to purchase my Portuguese 5001, I noted that the model my AD had in stock was equipped with the caliber 51010 with 44 jewels. The newer 5001 model year, according to the last IWC catalogue, has the caliber 51011 with 42 jewels and 21 600/h or 3Hz.

At first sight it seems very similar:

51010 from my watch:

[](s484.photobucket.com/albums/rr210/Mat-Vill/?action=view&current=w10.jpg)

51011 from catalogue:

[](s484.photobucket.com/albums/rr210/Mat-Vill/?action=view&current=Caliber51011.jpg)

At that moment, I wondered if is a good decision to wait for the new model since the 51011 probably be a improved version of the 51010 and may be will has a better performance. But then I thought that the only difference could be a tiny improvement in accuracy and with the simple idea that 44 jewels are better than 42 jewels (may be a wrong idea) I went for the 51010. Anyway I am so happy with my Portuguese with the caliber 51010 and it’s 44 jewels that all theses issues are just curiosity.

So, now I wonder ¿what are the differences between Caliber 51010 and 51011? ¿What was the year production for each one? ¿Why the improved movement have less jewels? ¿Is 51011 really a improved caliber or a minor cost production caliber?

Just want to learn more from your answers.

Kind regards,
M

There are several articles in the archives

You will find your answers there, I believe.

Bill

There are several articles in the archives

Would you help me with the links, please? Hard to find for me as I am I new member.

Cheers,
M

The second photo looks like a 80110 Cal.

I don't think you posted the 51011 in the second photo. That looks like the 80110 from the Ingenieur to me.

Me too - you are correct (nt)

Here is a chart for you that explains ...

Mateo -

The chart above explains the differences (subtleties) between the various calibers in the 5000 family.

However, this chart pre-dates the movement your are asking about - however the last 2-digits, I assume "11" would be similar to the 50611 (in the forunner column) used in the Perpetual Calendar that you see listed on the chart - it is a 3 Hertz. The net difference is listed as the "oscillating system" - which is essentially the difference between the 44 Jeweled 51010 (with 2.5 Hertz balance) and 42 Jeweled 51011.

If you click on the "search the archives" and type in 50111 in the "Message" field - you will find a lot of entries.

Thanks Richard...

I found this note with the adress you gave me:

"Portuguese Automatics and the 42 jewel mystery...

I obtained some interesting information about why the movements in some Portuguese Automatics have 42 rather than 44 jewels. In the course of obtaining this information, I learned more than a few things about the history of Cal. 5xxxxx movements.
What follows is an unofficial report from an executive at IWC, which I have edited and slightly rewritten:
IWC’s calibre 5xxxx movements IWC have had several modifications over the last 7 years.
The movements from the first stage of development have calibre numbers with 4 digits (cal. 5000, cal. 5011).
Then modifications were done with the design of the automatic bridge. Those movements have calibre numbers with 5 digits (cal. 50xxx).
The third development stage was modification of the oscillating system (3 Hertz Balance with excenter-regulation). Those movements have 5-digit calibre-numbers which start with the numbers 51xxx.
The most recent development stage was done in 2007. The cogging of the complete wheelwork was modified. A smaller modification also was done to the bearings of the barrel: instead of the rubies, IWC now uses beryllium bronze bearings there. Therefore, the new movements have two rubies less than the older movements.
Therefore, reference 5001, the Portuguese Automatic, has been made with three movements:
--cal. 50010 => 2.5 Hertz movement, 44 rubies
--cal. 51010 => 3.0 Hertz movement, 44 rubies
--cal. 51011 => 3.0 Hertz movement, modified cogging, 42 rubies"

From MF

Now I am pretty clera about it.

regards,
M