ϡ

ϡ U+03E1, ϡ GREEK SMALL LETTER SAMPI ← Ϡ [U+03E0] Greek and Coptic Ϣ → [U+03E2]

• Ϡ (Š) — upper case

ϡ • (š)

1. Sampi, an obsolete letter of the Greek alphabet with a numeric value of 900 when used as a mathematical character.

• It was used in addition to the classical 24 letters of the alphabet to denote some type of a sibilant sound, probably [ss] or [ts].
• ϡ on Wikipedia.Wikipedia

• → Gothic: 𐍊 (900) (from the ancient T-shaped variant)