Thanks a lot for your reply.
As I understand from your post is that there is no way to get MAC address from Host ID, as there is always a missing part; hope I'm not mistaken.
By the way, the examples I used ini my first post are not imaginary examples, they are from real Sun Blade machines... I noticesd that the Host ID always starts with '8' (not '80') and ends (i.e. last 6 characters) with the last 3 octets of the MAC address
Thaks again