I'll get into the marks again a bit below, but this is broadly why I didn't want to get caught up in the combat/non combat idea. I think its a bit counterproductive to examining the origins of the blade form and is leading to some preconceptions that are perhaps not entirely supported. I think you are certainly asking the right questions - i.e. why does this form pop up. Although the conclusions you are drawing aren't ones I can fully get behind.
This is where I just have to flat out disagree. There are major differences that I've pointed out between the two forms.
- Use of fullering
- Use of blade marks
The characteristics of the straight sayf are quite different then than the older battle sword form. To say it is merely a copy of the older form without the former's functionality is difficult to support I think. If that where the case, there would be no reason to adapt the different hilt, no reason to lengthen the blade, no reason to do anything really other than increase the flexibility and even that raises some interesting questions...
There's also the interesting question of why flexibility is important in the dance... Because of aesthetics? Because flexibility used to be considered an important quality for selecting blades (in a combat/usage sense) then taken to an extreme for effect in the dance? As I recall you have mentioned in fact that the older style is quite stiff. So that produces another question, when and why the focus on flexible blades.
Just to touch briefly on the stamps again but I guess my original point wasn't expressed clearly enough...
It is not a question of local stamping versus European stamping. It is purely a question of why local makers used stamps clearly taken from a foreign context. The only logical reason is because blades with those original stamps were known, respected for their quality and thus the stamps and marks were worth the effort to copy.
I'm glad you agree about the fullers - if you take the battle sword as a pattern of sword production before the straight sayf - the use of fullering is then due to outside influence. Why was it adopted? Why was this style chosen and how did they gain experience of this form if they weren't using these blades from a foreign context? It's not the sort of choice that I can imagining happening "overnight" and requires as a pre requisite: contact, use and evaluation. All of this points strongly to the use of straight blades, from a foreign source, in an Omani context.
I've always found your efforts intriguing about this type and as you note your approach as always been from a certain viewpoint which I can understand. However I think the approach has certain inherent weaknesses (as do all approaches in varying respects). The main issue I see is that the pageantry viewpoint is inherently leading to often examining the form from the viewpoint of what the sword form is used for now and all that goes with that in a modern context - local production, local stamps etc. However that has left to the side the questions of origin. No matter if the blades are produced locally and the stamps locally done as well - where is the vector, the point of change which caused this to happen? Why such a close coincidence with European trade blades? Again, for me personally, its a little much to attribute to chance. The central question remains, as it has over the course of these discussions for me, the point of change between the older form and the newer. The idea that the newer is simply a development of the older form is still I think tenuous at best for all the reasons highlighted above.
Just a brief note when it comes to local sources and looking at modern versions of traditions like dance - I've had some experience with this in my own research areas. Unfortunately, and this is quite frustrating, the people inside the culture using a weapon are quite often not as interested in the history of it as we might be. The sort of detail we look for is often not preserved and I think conjecture over a period of several hundred years based on examining largely modern examples of a form is not conclusive. Particularly because you've noted that in a modern context the stiffer attributes of trade blades would not be desirable and thus unlikely to be encountered in the present day in the region - they aren't in demand.
This ties into your point about lack of evidence for an alternative to your theory - I personally think the evidence is there. It may be implied rather than a physical example in your hand - but it is there. From fullers to blade length. I've highlighted in past threads examples with likely European blades, always from collections and auctions outside the region. This ties directly into my point above - these are less likely to be encountered locally, going on all the detailed info you've given about the current situation of sayf manufacture and use - because nobody would want them now
Hopefully the museums will have some more info they can make available to you of documented, older pieces. Ideally something 18th century that's known to have not been rehilted or otherwise changed.