TPG For Ancients.

PCGS doesn't slab ancients.

NGC will slab ancients, at least, most classes of them. Their edge-view holder at least allows you to see some of the edge of the coin, and the grading scale is multifaceted to reflect the less-than-simple process of market-grading an ancient coin.

ANACS will apparently slab ancients, though last I heard they only did Roman; your Roman Provincial tet may not qualify.

ICG was the first company to actively slab ancients but seemed to be worse than others at mis-attributions, and their grading scale was iffy at best. Looking at their website they don't seem to do it anymore.

As a rule, ancients collectors generally don't like slabs. The prevailing attitude is that an ancient coin managed to survive the past 2000 years without the benefit of a slab and will probably continue to do just fine without one in the future. They also generally don't trust the slabbing companies to "get it right" as far as identification, attribution and grade are concerned (possibly as a result of early exposure to ICG's efforts).

Ancients collectors that want to buy an opinion on grade and authenticity often use David Sear's Ancient Coin Certification Service (ACCS) - they will authenticate, identify and grade, but not slab.