Density is calculated by dividing mass by volume. One mL is the same as 1 cm3.
D = m / V
= 1158 / 20
= 57.9 g/cm3
You can now use a reference table to determine what the metal might be, or if you know what the metal is you can use a reference table of metal densities to compare the values. If your value, 57.9 g/cm3 is different from the reference value then your piece of metal is not pure.
I am assuming that this metal is imaginary as its density is almost 3 times that of gold and more than 5 times that of lead.
The year 1158 was in the 12th century AD
2415
1223-65 = 1158
1158/20 = 57.9 gallons
MCLVIII
Passions - 1999 1-1158 was released on: USA: 22 January 2004
Jinul was born in 1158.
Wibald died in 1158.
Days of Our Lives - 1965 1-1158 was released on: USA: 10 June 1970
Dark Shadows - 1966 1-1158 was released on: USA: 2 December 1970
Santa Barbara - 1984 1-1158 was released on: USA: 6 March 1989
958+200 = 1158