I suspect Scubapro must have had some problem with that original purge depressor design as they redesigned it in later years. For a while SP added a device built into the purge button on the G and R series but that fell by the wayside also. I suspect the realized such a device was counter to their more recent policy of annual dealer service. In any event, anthing soft that can be inserted between the metal and rubber cover will do the trick. My favorite is a 2" piece of soft tubing that goes completely across the exposed rubber cover. I store all my regs except the D-series (coaxial valve) that way. The unbalanced design benefits the most. The balanced barrel poppet design still gets over 50% of it closing force from the mechanical spring so it helps there also. The coaxial valve on the Air1 and D-series looks like it gets less than 25% of its closing force from the mechanical spring so the benefit is relatively small. Plus, the D-series design does not lent itself to depressing the purge during storage.
If you are into annual service, it probably does not matter at all. But if you are looking to maximize the time between service, it can really help.
