It's Fenix PD35, now discontinued. It's got a much tighter beam that the HL55 so it's useful for spotting, and it uses the same 18650 battery.
Thanks for the photos. I've one of those rubber bands I use with a pixa, they certain hold that very well. I'd not thought of putting a fenix on a petzl headband so may well give that a go.
Having said that I bought the fenix light about 2.5 years ago, use it at least once a fortnight, probably more and it gets a good bashing. The 'as supplied' headband is still holding up fine (much to my surprise).