Crystal & Base Metal (Spelter?) Oil Lamp; Flat-Ground Panels

This may have been my maternal Grandmother's; they lit with oil deep into the 1950's, an' she had literally dozens of them, some brought from the Netherlands in 1924.

The cast-metal base is six-sided an' unmarked, as far as I can see. It feels an' sounds harder than spelter; more like aluminum...but the lamp seems too old for cast-aluminum...I dunno, an' don't know how to differentiate between them. The font has 13 ground an' polished facets on what may be better than glass...but again, I am clueless about the difference between crystal & glass. It is un-reactive to UV. There is one 5/16 by 1/8 inch bubble on the cusp of two adjacent panels, if that may be useful. It's fitted with what looks like a #2 threaded brass burner ring, which I believe may be a replacement because of the plaster remnants in the threads, as well as its slightly uneven position on the font an' excess plaster inside, beneath it.

It s 8 3/4" high, ~5 1/4" diameter at the font shoulder; the base is ~5 3/8" high, 4 1/2" across the hex flats. It weighs 26 3/4 oz.

Any recognition of nation of origin, maker, pattern or age will be most welcome, an' all your comments are deeply appreciated.
Thanks for lookin'!