The numbers of the teapot
Most of the numbers associated to teapots I found in the web are lot numbers which are an identification assigned to manufactured single pieces. For example, these two Chinese Yixing teapots have each a lot number respectively 1078 and 1434.
In addition to the previous examples ''Utah teapot'' made by the computer designer Martin Newell
is associated with a catalogue number X 398.84.
The Igenix kettle has a capacity of 3.5 litres , therefore 3.5 could also be a teapot number.
The fourth example is the certificate of authenticity which is included with a pot and contains an authenticity number such as 5090.
link1:The source of the pictures
link2:Utah teapot number
link3:Igenix Corded Catering Kettle
link4:The authenticity number