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'.

This is a transcript from The Hound of the Baskervilles feature length episode from the Return of Sherlock Holmes TV Series. The butler, Mr. Barrymore, has just let his new master, Sir. Henry Baskerville know that he and his wife were planning to leave and open a business (most likely a pub). It is a big deal because the Barrymore family has served the Baskerville family for generations. To assuage any concerns of ill will Sir. Baskerville warmly asks "Might I look forward to you pulling me a pint in your own house one day?" This is also a big deal for the master to suggest that he would visit the servant and be guest in the servant's house. It levels the class difference between the two men. When Sir. Baskerville then says, "Mind you call it Baskerville arms?" he provides an extraordinary gift by offering permission for Barrymore to use his family name, which only he has a right to, as the name of the pub "Baskerville Arms." This is very prestigious and generous offer from a titled nobleman to offer his servant. It should be noted that Sir. Henry Baskerville grew up in the United States and Canada and may be more generous than most in offering this gift. So it is not a negative statement but an offer to let him call his pub "Baskerville Arms."