The weigh-in. What makes my BP Edition "Le Petite Prince" so heavy?

So I decided to compare the weight of my 500908 (supposedly without a soft-iron inner case) to my 500401 (that does have a soft-iron inner case). In an effort to eliminate as many variables as possible, I removed the straps and clasps from both watches and weighed them on a scale that had been zeroed and set to grams. The results:

500401: 115 grams.
500908: 118 grams.

I had expected that the 500908, without a soft-iron inner case, would weigh less, but it weighs more. Is it the dial that is heavier? Does it have a thicker stainless steel case? Is the C.51111 heavier than the C.51110?

Hi Ben
5004 has indeces and numbers painted in lume directly on the dial.
500908 has applied numbers and indeces, the hands are far more complex and the base metal for the blue dial might be different.
I'm guessing that the combination of all the above accounts for the extra grams.

Thank you Mark, I forgot about the applied numbers and indices. And the dial probably is heavier, but do you think these would cause a watch to weigh more than such a similar watch that has a soft-iron inner cage?

Well! There's only one way to solve this conundrum about the soft iron core: remove the case back,and let's have done with the uncertainty.

Well! It's official: The BP 500908 doesn't have a soft iron cage. How do I know this? i went to visit the IWC boutique in Kuala Lumpur, Malaysia,where I'd purchased my pilot chrono 377704 two years ago, and I asked the boutique staff about the doubt that surrounds the iron cage in the BP.Does it or doesn't it...... The salesman offered irrefutable proof that indeed the 500908,does NOT have a soft iron cage fitted. IWC supply at least to their boutiques,WORK BOOKS. These compendiums encompass all the models that IWC have currently listed for sale. All the technical information about each model is listed. BP500908 NOT FITTED WITH SOFT IRON CAGE.Why isn't a cage fitted,only IWC can answer that question.I hope they do offer an explanation.

The cage is formed by 3 soft iron components: Dial, case ring and inner case-back. If any of these is not iron, the watch cannot be described as having an antimagnetic cage.
In the case of the 500908 and 500906(BP Father) it was deemed necessary to make the dials from Brass, possibly for printing/production reasons. They are both fitted with the same soft iron case ring and inner case-back as other 5009's so should weigh the same.

Thank you so much Leo, that explains it! I had not seen your reply until now but it is very much appreciated.

The antimagnetic components obviously make sense, but what has really got me fascinated is the information pertaining to the dial. What other metals other than brass are used? The markers & indices are also a very interesting factor when considering weight, never thought them to matter that much. Thanks for a great little read.

The IWC pilot's watches that are anti-magnetic (or amagnetic as Michael always says) have dials made of iron to complete the soft-iron inner case. Revisiting this question now, I see that Mark was 100% correct! Brass has a higher density than iron and that, combined with the weight of the applied rhodium-plated numbers and indices, certainly explains the difference in weight.