[Jim McDougall]

This is an INCREDIBLE sword!!!
I have been watching the series "Outlander" on Netflix, which though a 'romance' oriented story, it portrays the Scottish Highlands in the 18th century prior to, during and after Culloden.

Obviously my family heritage (McDougall et al) is from there (we had men at Culloden, but other clan names). The Jacobites had ties to Italy of course, and Prince Charles Stuart himself was born and raised there. While France was of course the key staging area for the 1745 Rebellion, the Catholic Faith, with the Vatican was naturally the revered center religiously for the Stuarts.

Here the blade form is clearly an early blade with phrases in Latin.
I found the marking in "Small Arms Makers", Robert Gardner, 1963, p.360;

It is to an unidentified armorer in Venice, from one found on a 'salade' helmet c. 1465(pictured). It is important to remember that armorers attended to overall outfitting with armor as well as weapons.

The attached image of the mark cites as a source 'Keasby' which is unknown to me (not in bibliography).
The recessed ricasso does seem unusual on this blade, which may be of course an Italian arming sword, but perhaps with a developed guard system of this period.

This may be a heirloom blade acquired by a Scot in the service of the Stuarts in Italy, and held by an ancestor in distinguished lineage, who likely had the sword itself (or perhaps just the blade?). Perhaps he was serving in India and had the blade mounted in this traditional basket hilt in silver.

Another possibility would be that the sword blade was already in India, as European trade was prevalent of course, and Italian swords, blades etc. (typically Venetian, key in Italian trade) were often notably acquired.

With the inscribed phrases, the primary of course PRO CHRISTO ET PATRIA (for Christ and country);
but FIDE SED CUI VID (loosely, 'have confidence but be careful in whom you trust' ) was a favored phrase notably on the armorial bearings of the NICOLL family).
The NEC TEMERE NE TIMIDE (= neither rashly nor timidly)

Clearly a blade which would have been treasured by a Jacobite owner, as well as by his descendant.

An amazing sword with profound historical potential!