Hello Jim, and thank you for the superb references and general round up with a great couple of pictures of the Omani Batrtale Sword often called Sayf Yemaani. These are sometimes referred to as related to Swords Of The Prophet and your illustrations are covered in typically Omani decoration and even a hint of a zig zag at the edge of the cuff. The three holes in the hilt handle were apparently for rivets through a central core of wood and the top hole was for a wrist cord apparently. The sword example in the Al Ain Museum has the two holes in the shoulder of each Quillon as a decorative anchor point for silver adornment. These short stiff chopping and slashing blades were used in conjunction with the famous Ters Rhino hide shield. The weapon like so many Arabian weapons didn't evolve or change since it worked thus over centuries it has remained the same except when Saiid the Great had it immortalized with the Iconic Royal Hilt in a similar way to the Royal Khanjar.
Given that this may well be a relative of the Sword of The Prophet and as you note
it seems most likely these are Ibadi and of Nizwa origin. There is a strong possibility that the weapon came along with the religious form or in its wake...and that would indicate an earlier date possibly around 751AD and with Ibn Julanda the first Immam and Leader of Oman. It therefor becomes very tempting to suggest an earlier date of say another 100 years making this weapon style close to the actual passage to Oman of Islam ...and likely to be strongly associated with Nizwa the religious centre .
The other key EAA pages to consider with this conundrum are
http://www.vikingsword.com/vb/showth...t=Sayf+Yemaani
I place similar Examples and one with an as yet untranslated roundel style stamp and with the zig zag line as your sword shows. The grip and Pommel follow a Mosque/ Minarette style with multiple sides and the unmistakable arched pommel dome.