Sterling (?) cross pendant from Mexico

I purchased this cross from a vendor at the Mercado de Artesaniás in Ixtapa, Guerrero, Mexico. The stamp on the inside is hard to read, even with the magnifying glass. It almost looks like 824, 874, 925 (if the numbers are over the edge, and there is a very thin gap between the top of the 5 digit, and the top of the semi-circle of the 5 digit). The pendant does not respond to a magnet. It measures about 1 ¾ inch (see picture with the ruler and the blue background). I think I paid around $25-$30 for it, but I’m not positive as it was at least two years ago. The base metal appears to be at a slight angle, as well as the top, bottom, and one side aqua-colored stones, but all the stones are securely in place. Close inspection (with a magnifying glass) shows the transparency of the stones as slightly dirty/dusty, one has a slight bubble, and the edges of one seem to have some black dirt. The stones are a sky blue color.