Well that’s a cracking padlock and totally unexpected. It’s not the radial slider climax type I was expecting it to be, but it’s even stranger being the first of the ACME type that followed later.
Was all ready to say that Cotterill’s are always marked as such and that it’s the generic copies that are anonymous without makers name, but that being a Cotterill ACME patent type but signed Phillips & Son makes it a mystery to me.
FWIW, all of the climax detectors we saw on Phillips’ safes were only ever the generic copies and not Cotterill’s signed locks. Their escutcheons would reference the climax detector patent but IIRC never use Cotterill’s name, but seeing your padlock there suggests a possible tie-up of some sort between the two unless ACME patents had expired and that too was copied.