Small String of Graduated Knotted Pearls, Silver Clasp

It's 20" long without the clasp; weight is 19.7 grams; pearl count in the string is 79, plus 1 on the clasp. I'll risk assuming these are cultured. The last pic shows them partially illuminated by UV at the left; all other pics are in overcast natural light.
These were in with several pounds of costume jewelry, a moderate bit of which may have some eBay value...tho' I don't know enough about any of it to craft adequate descriptions. I'll just say what I see about them, an' list 'em. Anything of obvious value will show up here first, begging for y'alls generous expertise an' assistance, over the coming weeks.
Is there anything obviously worthy of note in this string? Unmarked save for the 'silver' on the clasp; could they be Mikimoto, or equivalent?
As always, thanks for lookin'!

 

Could be Majorica.

 

If they were Mikimoto the clasp would have their mark.

I have had costume pearls knotted so the string doesn't tell. Have you done the tooth test?

 

a stamp that says just...silver.......????

 

Not surprising if it just says "silver"; a lot of Asian export cultured pearls had that exact clasp. I'd bet on Japan for origin.

 

Yup...very lightly gritty.

 

My guess is older Chinese/Hongkong.