What's inside a 100 jeweled movement?

[markr]

Disappointment.

[watchweasol]

A bit of an overstatement and nothing more than decorative than practical.

[Nucejoe]

Yup,  Eigthy non-functional syntheric jewels. 

[oldhippy]

I've seen that sort of crap in Russian watches back in the 70's & 80's 

[KarlvonKoln]

Watches with "One Hundred Jewels!!!" consist of misleading advertising aimed at gullible laymen with deep pockets who don't always know the real reason watches have jewels, and have been duped into thinking "more is better".  The average watch just doesn't have that many pivots and escapement parts to put one hundred jewel bearings on.  Maybe if you had a musical alarm minute-repeater with automatons and day, date, moonphase, leapyear, car wash, and sundry other complications, you might need that many bearings.  But otherwise it's just added decoration to raise the price.

Edited June 3, 2021 by KarlvonKoln

[jdm]

6 hours ago, KarlvonKoln said:

But otherwise it's just added decoration to raise the price.

The many extra jewels of the watch in the OP where certainly selling gimmick, but not really decorative. Their technical justification was to lessen friction from the rim of the weight to the plate.