Was over at a buddies shop recently (semi retired and his half of the shop is now in his back yard) having some work done on my bat house mold. Noticed the number on the head of his newer Bridgeport and asked him "Is this a model or serial number?" "I don't know" was his answer. The other much older Bridge port had a random six digit number starting with '2' so I assumed these were serial numbers.
Once I got home a quick Google search confirmed my guess as well as some discussion trying to establish a correlation between the machine serial number and the heads separate serial number.
Long story short, my friend has J head number 300,000.