Complex sentence: By shortly after 700 highly elaborate large brooches in precious metal and gems were being produced, which were clearly expressions of high status for the wearer, and use the full repertoire of goldsmith's techniques at a very high level of skill.
Split into simpler sentences: By shortly after 700, highly elaborate, large brooches in precious metal and gems were being produced. These were clearly expressions of high status for the wearer, and use the full repertoire of goldsmith's techniques at a very high level of skill.