[Jim McDougall]

In order to better respond to the original query in this thread, I spent some time reviewing resources at hand to learn more about what types of swords were actually used in Sri Lanka from ancient times into more modern.
Turning to "Sinhala Weapons and Armour" (P.E.P. Deraniyagala, 1942, p.115) where he notes , "..it is interesting to note that among the 26 kinds of swords used by early Sinhalayans are those of Pandi, Vaduga, Malaya Telugu, Ayodhya and Java".

In his article Deraniyagala illustrates with line drawings a range of sword forms as seen primarily from iconographic sources such as friezes and frescoes with some as early as 6th ranging into the 12th, then again 16th and 17th. The earliest forms are described as leaf shaped, straight and double edged noted as being 'offensive' weapons.
Other types of blades including long straight single edged as well as wavy, saw edged and choppers are described, which of course would reflect the forms of many of the above listed regions.

With its importance in the export of fine steel in the trade networks of so many cultures and foreign powers it is not surprising that such diversity would be reflected in the armouries of then Sinhala in their swords .

Viewing many of the line drawings as well as examining some of the profiles of swords in "The Indian Sword" (P.Rawson, 1967) it is clear that there are distinct similarities in many of the forms to those of the Indian mainland.
Many of those with angular and lozenge shaped points resemble some of the Nair forms of India, as well as others from Andhra from Telugu speaking regions I believe . There are others which resemble forms seen in the iconography at Ajanta and Ellora from as early as 5th century, which profoundly reflects the connection via the Buddhist Faith in Sri Lanka and India.

Deraiyagala includes in the scope of his panoply of sword forms, the recognizable kasthane, which he feels begins in the 18th century with the influence of Arab sabres and he claims the lionhead comes into fashion.
Naturally it appears that this assessment is quite conservative, and it seems remarkable that the influence of Arab 'scimitars' as he calls them, would have taken this long to take hold.

Returning to the subject of the previously discussed kasthane alleged to provenance from the Hasekura mission which returned to Japan in 1620, in the article of November 15,1998, "Unique Kastane Sword in Japan" by Dr. P.H.D.H.DE Silva, there are interesting notes to another example .
It is claimed that two other examples of two other carved ivory 'simha head' hilts exist, one in the Victoria & Albert Museum in London, is believed to be a gift to the Chief of the Weerasinghe family by King Parakrama Bahu VI (1415-1467).

While this is tempting to accept this period as the earliest date for the noted lionhead hilt, as well as the example from the Hasekura mission c.1620, we must consider even these respected museum provenances as probabilities rather than conclusive evidence .

Returning to the spectrum of Sri Lankan swords from earlier periods and outside the prevalent kasthane analysis, we look to another article, "Two Old Sinhalese Swords", (by C.M.Fernando, 'Journal of the Royal Asiatic Society, Ceylon Branch, Vol.XVIII , 1905, p388-91).
There are two old swords said to have inscriptions from the Kotte period c.1374 AD These swords and the translations on the inscriptions were examined by authority P.E.Pieris who commended the translations, but felt the swords were much more recent, and 'European' about 300 years old.
Incredibly these are clearly Indian swords with dish pommel and knuckleguard resembling tulwars of probably 17th c.

This is what I mean about museum descriptions often optimistic if not in many cases, almost fanciful .

In the earlier part of this thread, we listed a number of references which pertain to the swords of Sinhala, and I hope this rather incomplete overview might give a least some perspective on the type of swords probably used in Sinhalese history. As indicated most of this can only be surmised as even iconographic sources may be imbued with a degree of artistic license, as well as our pervasive focus on the kasthane which carries a great deal of speculative analysis.

However these are the things which comprise discussion, and I fully believe that suggestions, observations and material presented must be regarded as evidence to be considered, and respectfully analyzed objectively.

For me, the subject of the esoterica of Sinhalese arms, particularly the swords, have long been a fascinating topic and often visited over the past 15-20 years. I very much admire the tenacity and knowledge of all who have participated in this thread, and sincerely hope we can all continue looking into these arms. There are so many questions yet.