Most of your items are horse-harness studs. The one at the top centre
had a small loop, which is now broken, which likely supported a small suspension pendant. The bottom left item might be the remains of a
fibula - I can't quite make out what is on the
reverse.
There are two possible decorative technologies here. Enamel
work is the
glass paste. Put on in paste form and then fired to make it glassy. Some of these might also have used
millefiori (
Italian for thousand
flowers) which is where fancy
glass rods were made - by wrapping very thin
glass rods of different colors together into a single rod. This rod was then sliced to create thin pieces that could be fitted onto bronze items. The technology is
still used today, especially in Murano Island near
Venice.
These items generally date from mid-2nd to late-3rd century. In
Nicolay's typology they are
type B2 studs.
SC
PS. Looking at your image again, the blue in the bottom left item is definitely
millefiori and the dark parts of the bottom middle item might be too. The rest look like enamel.
