I had too much time to kill over one rainy weekend afternoon, so I decided that "enquiring minds want to know"... Today's question: Is A/6538 case really that much different from 6538?

First, a look at the mid case. Both A/6538 and 6538 look to be similar at first glance. But the raised rim on the A6538 (where the crystal sits) appear a tad higher than 6538. The rim on both my 6538 and 5508 are about the same height. This rim together with the retaining ring, creates a "groove" to keep the tension spring in place. But hang on, why is the rim significantly higher on A/6538 when it doesn't appear to serve any purpose? ie. no tension wire used on A/6538.

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Maybe a closer look at the retaining ring will give me an answer. A/6538 retaining ring is much more robust compared to the flimsy thin ring found on the 6538. The shape resembles the conventional 5513 retaining ring. My guess is MOD wanted a bigger bezel on the sub. Bigger bezel means taller crystal ie. T19. I did not have a micrometer on hand except for a pair of calipers. It seems to me that T17 and T19 have same inner and outer diameters, which means a T19 will fit onto a 6538, but just sitting higher.

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Curiouser and curiouser. What is the purpose of the higher rim? And why doesn't Rolex just make a retaining ring with the suitable dimensions rather than changing the original 6538 mid case and adding a ring on top? No change to original 6538 design, while accommodating the taller bezel. Something like 5513 mid case and retaining ring design.

Next, the bezel. OK, we know the A/6538 bezel looks similar to it's successor, the 5517/3 milsub. It is larger with flared sides, compared with "straight cut" bezel found on 6538. And it no longer uses tension wire which clips under the edge of the retaining ring. But flip the two bezels over and it's a whole weird story. The A/6538 bezel must clip on the retaining ring and at the same time cover the "useless" rim on mid case. And even more surprising, the inside of the A/6538 bezel has no discernible ridges or grooves, unlike the 5513 bezel. I am indeed surprised the bezel did not fall out when the MOD officer shook his **** after taking a pee!

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My conclusion, the afternoon demonstrated an exercise in futility as I did not gain any further insights into the anatomy of this watch.

I would love hear any views from you chaps.

Now I shall relief some stress by enjoying a few of my other favourite shiny toys, and return to my usual "lurker" mode

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I do enjoy tedious weekend afternoons... it's amazing what you can learn when left to your own devices!

I guess I need to invest in a good set of callipers and a white lab coat, and then invest some proper time scientifically studying my bezel collection...



MW

on rainly days though LOL!

simply the mother of the 1665 one ( it has same height of the oldest bezels for early 1665 ) :

Yes, the A/6538 bezel is higher than 5513. I would summise the rim of the case adds "height" to T19 allowing for the taller bezel.

But was this really necessary? Or is it because the larger bezel (required by MOD) needs to be "raised" to clear the oversize crown.

Which means the taller bezel was a by-product from a pre-existing design and not an intended design in itself.

I may be over thinking this

Thanks again.

I have shown has a tropic 17 glass instead of the 19.
here is the Revolution A/6538 with the tropic 19 :

( thanks Paul !! )

for the over-sized bezel on the A/6538. I can well believe the British MOD would demand a practical and usable bezel on a 1950's diving watch, and until the design and construction of the dive watch was refined, a chunky easy-grip bezel was a necessity.

Rolex progressed quite a long way with their diving watches in 20 years!



(Left to Right: 5513 (Navy) ~ 5513/5517 (Navy) ~ A/6538 (Navy) ~ 5517 (Navy) ~ 5517 (Army))

MW

I have been educated this afternoon

Comparing the bezel height on the A/6538 with a 1967 Patent Pending Sea-Dweller, they do appear to be the same, although the profiles are somewhat different...





MW

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This bezel and the one shown by Marcelo above look much the same.

Paul's (from Revolution) and Mike's look much the same.

But when I stacked them alongside each other, the two sets don't quite match up... Am I seeing things?

are you meaning that the one I have posted and your look made in two different parts and the other two look "monobloc" ( as there is no gap between the lower and the upper part ) ??

Ours look a bit like a pie with "crust" on top. The sides are also a bit curve, again like a pie.

Whereas the other two look like, as you said "monobloc", and with straight sides.

At first I thought mine could be due to wear-and-tear, but after seeing your post, now I'm wondering if there were two kind of bezel variants made for MOD. I must admit the other two looks like better manufacturing (and possibly slightly different alloy mixture).

I really just guessing here

Thanks again for your invaluable input.