This post is intended to clear up some confusion about Hammond Manufacturing brand transformers and their date/lot code markings. Hammond places a time stamp on their transformers at the time of manufacturing and another time stamp on the box when packaged and these are not the same. These markings, since a transformer does not have any shelf life, would be used only for product traceability and warranty purposes.
When looking for a marking for either of these purposes the marking on the transformer itself is best, however either marking will suffice. The markings in question are a four digit code in the WWYY format. See 160D24 and the following images for example.
If there are any questions on this, please reply to this post and we will be happy to address them.