We get asked all the time "Can I fit a new GMT IIc Bracelet to my Sub 16610" (OK, it's not always the Sub...but that is the example today)
The short answer is Yes...but with conditions..... and these conditions are a bit different for other watches..
First, let me say that the 78200 bracelet is a direct replacement with the Daytona 78590 except it takes a 2mm spring-bar and the Daytona takes a 1.8mm spring-bar - but they are so close the fit is very comparable. The main difference is in the SEL.. The spring-bar diameter is no small difference... You must use the 2.0mm spring-bar with the 78200 and the 93250, whereas, it simply will not fit through the smaller 1.8mm diameter tube hole of the Daytona 78590... You use the spring-bar for the bracelet...not the spring-bar for the watch !!
Back to the project at hand; a GMT or Daytona to a Sub Date...
The Sub 16610 has an SEL 93250, and the root (thickness of the bracelet where it meets the case side) of the SEL is 4.5mm thick. The GMT 78200 has a root thickness of 5.5mm, so there is more meat on the GMT bracelet; the Daytona 78590 also has a 5.5mm root.....this will make it fit differently.
Inside the two bracelets are somewhat different at the SEL, as mentioned.
The backside of the GMT 78200:
Backside of the Daytona 78590...notice the central angle and blend is very different.
Another thing to note is that the Rolex SEL has two flanges... On the 78200 and 78590, these flanges are quite thick...almost twice the thickness of the typical bracelet SEL:
The flange thickness is interesting because the Daytona and the GMT both have machined lips on the back of the case to accept the thicker flange.. Other Rolex SEL cases have the shallower lip to capture the SEL, including the Sub-Date. Of note is that the Sub 14060 has no flange lip and a Rolex SEL will not fit..
This shows the deeper SEL lip on a Daytona:
Here we see the shallow SEL lip on a 16570. It is the same as the Sub Date 16610:
Either of these bracelets will mate up to a 16610.. Oddly enough though, the Daytona Bracelet, using a 1.8mm spring-bar fits a little high and produces a lip at the top of the lug..
Perhaps this is variable with other samples. It can certainly be filed to fit, and it may not interfere at all..
Both bracelets, due to the larger flange we discussed, and the shallow lip, will not fit flush at the back, but will have a prominent lip.. In use it is not really an issue and extends no more than the early hollow end links:
So.. What have we learned..
It is possible to update your flat channel, hollow center link Sub Date to a more modern solid center link, and billet clasp bracelet. It is a direct replacement. However, the actual fitment is not precise but completely serviceable and can give new life and comfort to an old classic;;