Short answer:

The more lurid the tale, the more skeptical you should be. . . and this one is pretty dubious. But it is a nice historiographical rabbit hole, leads us down a path of "how do misapprehensions become accepted as real, and how physical objects get appropriated into these narratives as 'evidence' for something they're not.

Discussion:

Who doesn't love a museum of torture? Certainly not any "quaint olde" European town with a Black Museum to beguile tourists. What to put in that museum? Genuine brutality wasn't rare-- witches, Jews, heretics etc all met horrible fates in both the distant and more recent past, but typically there's not much to look at. So we need a "witch's chair" like the one that alchemist Anna Zieglerin was purportedly (but probably not) burned in. And and enterprising blacksmith can whip up some old-timey chastity belts as well . . .

In the 19th century, a healthy business grew up selling lurid bits of hardware-- you could see it as a descendant of the equally dodgy business in Saints' relics of years gone past.

In his 2007 work "The Medieval Chastity Belt: A Myth-Making Process", Albert Classen argued that there were essentially no chastity belts, that the entire thing was a myth. Classen, a German scholar now at University of Arizona, does a really thorough job chasing down quotes, examples and illustrations that are represented as authentic chastity belts and debunking them.

We do find some examples of people writing about such things in years past -- but it seems more in jest than in earnest. So, for example a German of 1405 describes a chastity belt as "an apron for Florentine ladies" . . . which seems more a bit of national stereotyping than anything serious; but people were at least familiar with the idea. But whether the idea "you should lock it" actually translated to any real lock? We don't have much evidence for that.

Classen also puts the chastity belt in a philosophical category: along with mistaken modern notions that medieval folks were prisoners to the flat earth theory the chastity belt "draw[s] from a mythical concept of the past which relies on a false interpretation, or on fake objects, most likely in order to [pat modern readers' on the back for] our scientific, social, and political progress".

Classen has some critics, folks who argue that perhaps not all the examples were spurious . . . so perhaps it happened sometime, but the evidence is-- it was very rare, if it happened at all. To the extent that physical object did and do exist, they seem to be relatively modern, the erstwhile "medieval" objects probably dating to the 19th century

With respect to the _real_ imposition of chastity-- it did happen, principally to men, through the unhappy mechanism of castration. Eunuchs were common in several civilizations -- China, the Ottoman Empire are well known examples. Various forms of female "circumcision" also served this purpose, and sadly did and do continue to exist.

Sources:

Classen, Albert. "The Medieval Chastity Belt: A Myth-Making Process" (Palgrave :2007)

Nummedal, Tara "Anna Zieglerin and the Lion's Blood: Alchemy and End Times in Reformation Germany: (University of Pennsylvania Press:2019)

Bishop, Chris. "The 'Pear of Anguish': Truth, Torture and Dark Medievalism", International Journal of Cultural Studies, 2014

West-Harling, Veronica Ortenberg. "Medievalism as Fun and Games", Studies in Medievalism XVIII, 2010