Silkworm Gut Sutures The dark blue cardboard case contains a clear glass jar with a black plastic lid. The white label on the jar reads in black ink: 'I.S. Sterilised silkworm gut, size fine, 50 x 12" strands in 5% carbolic solution,' along with 'International Sutures Ltd., Greenford, London, England.' The same label is present on both the cardboard case and the glass jar. The 'I.S.' logo is also present. At the bottom of the case there is a cotton pad. 1925-1975