It is hard to say without context, but at a guess, this is someone telling another person to be careful to use the correct name when referring to something - although it seems odd that 'arms' is not also capitalised. "Mind that you call it......" is a way of saying, be careful, take care, be mindful when you say the name that you say it correctly - perhaps there is some sensitivity about using the correct terminology. "Baskerville arms' could be a Britsh pub (but the Arms should be capitalised) or, the person could be referring to a coat of arms for a family called Baskerville - but then it should be 'the Baskerville arms".

When asking questions here, it always helps to give context to a question. Often an expression only has meaning in context - the context of the age of the writing, and what went before. I just googled it, and found that the phrase only appears in very few pages, so I wonder if it has been copied incorrectly. Can you give a link to where it is from? Without that - I can only guess. 'Baskerville' suggests it is from Sherlock Holmes. My guess is that 'mind' means to take care, or to ensure. 'Baskerville Arms' sounds like a proper name, 'Arms' is often the name of a pub. So - it sounds like someone is telling someone else to be careful to refer to some place as 'Baskerville Arms'.