Series I bass for sale in Australia
http://www.ebay.com.au/itm/1981-ALEMBIC-Series-1-4-String-Fretless-Electric-Bass-Guitar-w-Case-/201509611361?hash=item2eeae8a761:g:3nEAAOSwCQNWdGwv
 
looks like it was a standard bass that had the frets removed.  
 
 
 
 


 
 
Interesting thing about this is, I've been looking for ages and soon as I buy one, others start appearing online with dark woods which has always been my preference.!
Timing is everything....

Where is the serial number supposed to be?

Likely stamped on the end of the neck between 24th fret and end of fretboard or inside control cavity.