I don't recognize this bead.

I am inclined to disagree with the information posted by the seller. I would not call this a "large" bead, and I don't know how it can be attributed to the "late 1800s." If it's a Venetian bead (a prospect I am not convinced is true), it is more likely an early 20th C. bead.

The features that make it look odd are that the white layers are unusually thick, allowing the red and blue layers below to remain unmolded/unstarry. I have documented a few Venetian chevron beads that are similar. In addition, as Joyce noted, the color of the external glass appears to be nonstandard. The tone is grayish and more translucent than usual. Then, the shape of the bead is unexpected. It's sloppy and inconsistent, in terms of providing a standard rounded form.

Can you say where you have seen similar beads, and what it is that suggests they might be contemporary? That would be interesting information.

Unless the bead can be attributed to some non-Venetian industry, I would be more inclined to suspect it IS Venetian, but not from any of the usual manufacturers, such as Moretti or the Conterie (nor Costantini, as far as I know).

Be well. Jamey