Just a little more on the dating of these
gunong. I have taken the liberty of annotating one of Detlef's pictures.
The circled areas highlight the back edge just before the first "true"
luk. The lower example shows a straight edge with a sharp point immediately before the first curve. This is less obvious in the upper example. This sharp point of the lower example is also seen in the same place on Mindanao
kris from the end of the 19th C and into the 20th C. It is typically found on the heavier bladed versions of Maranao and Maguindanao
kris from that period. The upper example is of a style that predates this feature. That does not mean that the upper example is older, just that it is an older form.
Jeff's example at the top of this post also shows a sharp point at this area of the blade.
My (conservative) feeling is that all of these examples, mine included, likely date from no earlier than the 1890s, and most likely are from the first part of the 20th C. This is based on an analogy to Moro
kris showing similar features and the assumption that the ferrule/guard style was confined to relatively few (perhaps ony one) source. The construction of the combined ferrule/guard is unusual and requires materials and some expertise for brazing/silver soldering that may have been very limited in the Moro world of swords and knives. Some of the brazing looks fairly crude.