How old is my Steinway & Sons piano?

Steinway Model S Baby Grand Piano
Length: 5′ 1″ (155 cm)
Width: 4′ 6″ (137 cm)
Weight: 540 lbs (245 kg)
Scale Tension: 32,300 lbs
Introduced in: 1936
Available in: Mahogany, Walnut, & Ebony

Steinway Model M Grand Piano
Length: 5′ 7″ (170 cm)
Width: 4′ 6″ (137 cm)
Weight: 570 lbs (259 kg)
Scale Tension: 33,800 lbs
Introduced in: 1911
Available in: Mahogany, Walnut, & Ebony

Steinway Model L Grand Piano
Length: 5′ 10 1/2” (180 cm)
Width: 4′ 6″ (137 cm)
Weight: 610 lbs (277 kg)
Introduced in: 1923
Available in: Mahogany, Walnut, & Ebony

Steinway Model O Grand Piano
Length: 5′ 10” (178 cm)
Width: 4′ 6″ (137 cm)
Weight: 610 lbs (277 kg)
Scale Tension: 41,800 lbs
Introduced in: 1900
Available in: Mahogany, Walnut, & Ebony

Steinway Model A
Steinway Model A Grand Piano
Length: 6′ 2” – 6′ 4 1/2” (188 cm – 194 cm) (A3)
Width: 4′ 6″ (137 cm)
Weight: 695 lbs (315 kg)
Scale Tension: 41,800 lbs
Introduced in: 1878 (round tail “A”)
Introduced in: 1896 (square tail “A”)
Introduced in: 1913 (“A3″ 6’4” 1/2″ (194 cm))
Available in: Mahogany, Walnut, Rosewood & Ebony

Steinway Model B Grand Piano
Length: 6′ 10 1/2” (210 cm)
Width: 4′ 6″ (137 cm)
Weight: 760 lbs (345 kg)
Scale Tension: 39,000 lbs
Introduced in: 1872
Available in: Mahogany, Walnut, Ebony

Steinway Model C Grand Piano
Length: 7′ 5” (226 cm)
Width: 4′ 6″ (137 cm)
Weight: 882 lbs (400 kg)
Introduced in: 1884

Steinway Model D Grand Piano
Length: 8′ 10 3/4” (271 cm)
Width: 4′ 6″ (137 cm)
Weight: 990 lbs (449 kg)
Scale Tension: 45,400 lbs
Introduced in: 1884
Available in: Mahogany, Walnut, Rosewood & Ebony