archaic letter of the Greek alphabet

Sampi or Disigma is a mysterious Greek symbol. Its meaning is still debated today. Some believe it to be a replacement of 'san'. Before that, it was a letter that was used in the Greek alphabet in a few Greek cities in the 5th century BC. At that time, it looked like Greek Sampi Ionian.svg or Greek Sampi Pamphylian.svg. It was probably pronounced like "ts" or "tch" in the dialect of those cities. Over time, it was changed from Ͳ to Greek uncial Sampi.svg or Greek uncial Sampi 02.svg and at last to Sampi.svg. Eventually, the letter came out of use, while it was still used to denote "900" in the system of Greek numerals.

Sampi uc lc.svg
Greek alphabet
Αα Alpha Νν Nu
Ββ Beta Ξξ Xi
Γγ Gamma Οο Omicron
Δδ Delta Ππ Pi
Εε Epsilon Ρρ Rho
Ζζ Zeta Σσ Sigma
Ηη Eta Ττ Tau
Θθ Theta Υυ Upsilon
Ιι Iota Φφ Phi
Κκ Kappa Χχ Chi
Λλ Lambda Ψψ Psi
Μμ Mu Ωω Omega
Other letters
Ϝϝ Digamma Ϟϟ Koppa
Ϛϛ Stigma Ϡϡ Sampi
Ͱͱ Heta Ϸϸ Sho
Ϻϻ San