I've never seen one of these Italian blown glass diorama style indent scene Christmas ornaments that wasn't silver on the outside, blue on the inside. This one has a rainbow shaded red, green, and yellow gel tint coloring. I think it's an earlier version of the more common 1950s Italy diorama ornaments.
It measures just over 2 inches diameter. Inside the recessed front opening is a hand painted plastic Father Christmas style Santa figure in with a walking stick and yellow toy sack slung over his shoulder. When held to the light you notice a little inner mercury silvering loss, and the gel paint at the back is crazed (crackled) as shown. No chips, breaks, or damage.