TJW98LS interpreted that data as the minor change was indicated as a "1". That is not correct. Coil suspension ends in "0" and "1" notes air through the entire generation.

 

RA40 is correct - the "1" indicates Factory Air Suspension.
I would add that it appears that Lexus dropped the UCF31 designation for US models of the LS430. As far as I can tell, all US LS430s are UCF30, even those (having the Ultra Luxury package) with air suspension.
International models (at least in some countries) retained the "1" for air suspension.
So much for consistency :-)

 

Mine european 1998.06 has air suspension, but VIN number describes it as UCF20L. So still it's unknown what's differences between 20 and 21.