Kai, many thanks also for your comments.
I agree with you that labeling the gold hilts as kris (as some of them were captioned in the book/s) may be premature.
On the dating method employed, the use of excavated associated Chinese ceramics and pottery is actually a well-accepted method.
In any case
if I may recap the considerations discussed so far --
ARGUMENTS FOR A PHILIPPINE ORIGIN
[1] the specimen was found in the Philippines; thus at first blush it has to be regarded as Philippine, and the burden of proof is in proving otherwise
[2] in the dissertation, it is apparent that the panelists (the American university professors) concurred with the proponent (Dr. Dizon) that the specimen was a Philippine artifact
[3] one of the dissertation's key findings is that over time, the metallography of Phil. iron implements improved as expected -- now if the subject kris was an imported item, most probably its characteristics would not have synced (or is anachronistic) with this key finding
[4] linguistically and from time immemorial, "kalis", "keris", and "kris" have been established to be the Philippine's primary weapon, aside from the kampilan -- hence, the presence of an ancient kris in the Phils. should not come as a surprise (and the Indonesians and the Filipinos must have had a common linguistic ancestry: "sandata" [Fil.] and "senjata" [Indo.] both refer to weapon, "kalis/karis/kris" [Fil.] and "keris" [Indo.] all refer to the same blade genre, etc.)
[5] it was also seen above that experts from all over have noted that ancient Philippine craftsmanship (10th to 15th century) was at par with the Javanese - thus once again, the plausibility of the specimen being Filipino is very much there
[6] zooming in on the specimen itself, I think it's easier (at least for me) to imagine the thing to be morphing over time into a Moro sundang (kris), rather than it evolving into the more slender and pointy keris -- but perhaps this is a matter of opinion
[7] and then we have the square cross section of the tang, which is a distinguishing trait of the Philippine/Moro kris (vs. the predominantly round cross-section of kerises)
[8] then we also see in post no. 10 above the elephant's trunk/ bird beak in one of the gold hilts (plus the bird's head motif in the others) -- my point here is that these features as we all know are still present in Philippine krises, and thus we see a coherent picture over time.
ARGUMENTS FOR A JAVANESE OR INDO. ORIGIN
[1] raiding and trading were prevalent at the time; thus it's also very possible that the kris was obtained via those means
[2] of the 90 or so artifacts examined, there was only one specimen that is like the subject kris
[3] I suppose that there is a larger body of literature that pertains to the development of the keris as originating from Java
[4] though the keris' tang's cross-section is circular, a few early (or rare?) kerises had square cross-section.
Those are the pro-Java arguments I can think of. But the fewness of the points was certainly not to load the dice!
It's more because of my unfamiliarity with the Javanese keris. Hopefully, some of the other experts can chime in as well
PS - If anybody has access to the writings per attached, I think Guthe's own account can shed some more light on the matter.