Piece type
The piece most buyers mean by "vintage cast iron." Pre-1960 Griswold, Wagner and Favorite skillets had their cooking surfaces milled smooth at the factory, which is the main practical difference from modern sand-textured iron. Size numbers come from the stove-eye openings of wood and coal ranges, and they line up roughly across makers: a No. 8 from Griswold, Wagner or Lodge is about 10¼–10½ inches across the top, a No. 10 about 12 inches, and a No. 3 about 6½ inches. The No. 3, No. 5 and No. 8 are the most common sizes; the No. 14 and larger are scarce. On any skillet, check that it sits flat without rocking or spinning, look for hairline cracks from the rim, and watch for pitting, sandblasted finishes and plating.
19 hand-curated skillet reference pages across all five major makers.

typical $90–$220
c. 1920–1940

typical $50–$130
c. 1939–1957

typical $40–$95
c. 1939–1957

typical $180–$400
c. 1920–1940

typical $35–$80
c. 1939–1957

typical $55–$120
c. 1939–1957

typical $150–$350
c. 1880–1907

typical $70–$150
c. 1922–1959

typical $40–$100
c. 1922–1959

typical $80–$200
c. 1891–1922

typical $50–$120
c. 1922–1959

typical $30–$80
c. 1940s–1980s

typical $45–$130
c. 1940s–1980s
typical $100–$220
c. 1896–1910 (attributed)

typical $90–$250
c. 1916–1935

typical $70–$160
c. 1916–1935

typical $60–$150
Early 1900s–1940s (marked)

typical $80–$180
Early 1900s–1940s (marked)

typical $80–$180
Early–mid 1900s (approx.)