Hull Identification Numbers

[kwaltersmi]

Can anyone confirm what year hull indentification numbers (HIN) became mandatory? I can't find the HIN on my 1972 boat and was told that they weren't required at that time.

[arbarnhart]

Here is something that has some current regulations and notes that they were established in 1972:

http://edocket.access.gpo.gov/2004/pdf/04-13609.pdf

that would imply that they would probably go into effect after 1972.