It’s possible that you take your key to get some copies made only to be told that it can’t be copied, that it’s restricted. They might also say it has a restricted profile or is a restricted blank. There may have been a clue or two: a serial number or a telephone number on the original key. Such a key can only be copied by a locksmith with access to said restricted blank.
Customers who have have had this happen with keys they have inherited sometimes think it’s just a scam by the locksmith to make more money. Well, usually it’s not. Here, for example, restricted keys are considered a pain rather than a source of profit.
The normal reason such keys are used (and the reason we offer them) is in order that keys can be given to occasional callers, such as cleaners and dog walkers secure in the knowledge that copies can’t be made of those keys. So that’s the plus side: you know surreptitious copies are not being made of your keys. The downside is that you are restricted to just one source for your key copies, you have to pay more for those copies and sometimes there is a key card you mustn’t lose.
The downside for us is that there is no profit once we’ve paid the postage or made a delivery and we have customers who are newly occupying premises with such keys who suspect we’re on the make.