Is it a preset or an A.I.R. reg? If it's an A.I.R. - then it's fully adjustable from LP to HP (and vice versa). If it's a preset - then it's probably an LP.
Either way - Dusty is right - but I just thought you'd like to know a bit more .
the a1 will run on either, but you may want to test the output if its hp, lips do it for free, one bottle of mine, which is 6 months old was running close to 1000psi, which over the limit for most regs to handle.