Different manufacturing batches were made in different colours. Had there been more reported failures with say red coloured Univalves, then it would be easier to identify a problem with that batch. So Steve would know the date when, say, all the black ones were made.
So if someone said they got a black one from him 3 months ago, and it failed, he would know he sold that batch 4 years ago and hence that Univalve would be much older than his customer claimed and not be under warranty.
In the power tool industry, manufacturing date codes were extensively used, not only on the original tool, but also on each major component. This helped the German factory back then to identify any product that had developed a manufacturing fault. It also was a way we could identify if a customer was trying to scam us by swapping old parts from a failed power tool into the new one and sending it back for a full refund.
