The 1830 trap
For the most part, sellers on eBay are not happy if you tell them something isn't as old or valuable as they think it is. So it's something I rarely do. But there's one particular mistake I see about once a month. That's a seller who thinks they have a rosary from 1830.
The "1830" trap is easy to fall into if you don't know what you're looking at. Here's where you see it:
This is the front of a very popular Catholic medal, called the "Miraculous Medal," which turns up fairly often attached to, or as the centerpiece of, a 20th century rosary. There was a large upsurge of devotion to the Virgin Mary in the second half of the 19th and early 20th century, so there are lots and lots of these medals floating around. The date "1830" appears on all of them.
What "1830" represents is the date of the vision that inspired the medal: an apparition of the Virgin Mary to Sister (now Saint) Catherine Labouré, in the convent at Rue de Bac, Paris.
In a preliminary vision, Mary greeted Catherine familiarly and talked to her for a long time. A later vision showed Mary standing with her hands outspread, exactly as you see on the medal, with glowing letters surrounding her saying "O Mary, conceived without sin, pray for us who have recourse to thee." The vision then rotated to show the design for the back of the medal:
A voice told Catherine to have a medal struck after this pattern, and promised that many graces would come to those who wore it. To make a long story short, while Catherine herself remained unknown to the public most of her life, she succeeded in persuading her confessor and superiors to produce and promulgate the medal, which became instantly popular. Reports of miracles soon began to come in, leading to the popular name "miraculous" for the medal. It can be easily identified because the back is always the same "official" design.
The popularity of the medal, then, dates from the mid-19th century, as does (I think) the popularity of this particular pose for the Virgin, with her hands spread and "rays of light" radiating from them, representing graces. By itself, this pose is known as "Our Lady of Grace." Miraculous Medals have been struck with the 1830 date for more than 150 years now, and are still being manufactured today, so the presence of this "1830" medal doesn't mean the medal, or any rosary to which it may be attached, is anywhere near that old.
In point of fact, the vast majority of the "very old" "antique" and "vintage" rosaries on eBay are 20th century. Once in a while one does turn up that's clearly from before 1900, but it's not at all common, even for rosaries owned by someone's grandmother, or rosaries that are heavily worn.