On some of the surviving lifebelts markings in the form of stamps can be seen. As could be read in the lifebelt requirements, each one had to be stamped ensuring it was “Warranted to pass Board of Trade survey.”

Other additional markings have been observed on a selection of  lifebelts as well. Some examples have been stamped to identify the “FRONT”, the “INSIDE BACK”, and a Fosbery maker's mark can be seen on the front-bottom cork pockets. It would appear that not all lifebelts were stamped, but as can be seen with the Astor lifebelt these stampings tend to fade over time and become invisible to the naked eye.

The markings were added using a hand stamp on the flat linen fabric before the cork blocks were inserted, utilising either a dark blue or purple shade of ink. The exact color and size of the imprints vary between lifebelts, which shows that more than one stamp was used on the production line. Although subtle variations have been noted in the stamps themselves, they are all in the same style and all appear on the same cork pockets from example to example, suggesting there was a guideline to follow when marking the lifebelts.

Archival photos and newsreel footage of Carpathia stewards in white coats posing in Titanic lifebelts show that the flax linen used by Fosbery was nearly a pure white when new, so the purple or indigo stamps must have once stood out prominently.