Look inside the head, where the Battery ‘+’ goes, for little white letters that say “105-C”. If so, here’s one way to get the current regulation and single-mode operation.
Here’s a more detailed look at the driver.
To put it simply, it looks like, without having to remove the driver, to convert a 105c to Single Mode, the absolute easiest thing to do is solder a jumper between LED+ and VDD (RH pin of the 7135) at this point:
(Full disclosure, I haven’t actually tested this, except by accident; but the circuit is pretty simple…)