A British Thornton No P221 Comprehensive duplex plastic slide rule with plastic cursor. The 27 scales are: LL01, LL02, LL03, DF,
CF, C1, ISd, ITd, Td, Sd, C, D, LL3, LL2, LL1, S, ST, T, A, B, L, K, C, D, D1, Ps, Pt. the slide rule has been used but all of the scales are still clearly marked.
The slide rule comes in a black vinyl case, which has some scratches and scuff marks..