Anyone know how old these Ruben Craddock & Son cuffs are?

Hi. I'm considering purchasing a set of (assumed) Ruben Craddock & Son adjustable Darby handcuffs from someone who said he got them from a German collector. While he doesn't know the history, the following markings might give a clue: RCS 206 (with Ys around the perimeter of each cylinder) and 330 (near each hinge). Obviously, there is no date marked. Sorry to be so vague, but I have no further info. Thanks in advance for any replies. Tom Interval