Pontic Chalkaspidai and freed slaves?

[AqD]

Hi all!

Anyone know where the Pontic Chalkaspidai (brazen shield) come from? I saw they're mentioned in Plutarch's Life of Sulla and discussed in an old thread here but no clear answer.

Are the Chalkaspidai and phalanx of freed slaves the same unit? If not, where and how did the kingdom draw soldiers into the unit of Chalkaspides? Are they given lands in exchange for service? Are they professionals like later-period Macedonian Pezhetairoi or seasoned troops like Seleucid Argyraspidai?

Also in their unit description: "Vital to the success of the Pontic Chalkaspidai are light hoplites, hypaspistai, or even experience Persian light infantry stationed to guard the vulnerable flanks of the greater phalanx" - Where is their hypaspistai??