1 brass, metal or tin 19-20.
2 in plural tin cans 20.
3 ice 20.
4 wire 20. etymology: origin obscure doesn’t seem to be any connection with Scots mashlum ‘a mixture of several types of grains’; sense 1 also collected by Simson (1865); also attested by Galloway Tinkler-Gypsies; sense 2 attested by Galloway Tinkler-Gypsies; sense 4 attested by Perthshire and Argyleshire-Tinkler-Gypsies