Mine’s a gin and tonic

I encountered a sentence that's full of British culture:

I have found a pair of my father’s old tan driving gloves, the sort that say ‘Mine’s a gin and tonic’ and that my mother would have accessorized with her horsey headscarf from Country Casuals.

I found out that Country Casuals is a brand of clothing, but I don't understand what the phrase ‘Mine’s a gin and tonic’ means... I only know that gin and tonic is a popular drink in the UK, but what does the phrase mean here?

Also, I'm not a hundred percent sure of the meaning of 'horsey' too. The closest definition I believe is 'large and clumsy' but it feels a bit odd in this sentence.

Solution 1:

"Mine's a [name of alcoholic beverage]" is said in a pub when someone is buying a round of drinks.

Example

John: It's my turn to buy a round. What's yours Susan?

Susan: Mine’s a gin and tonic, thanks.

John: What about you Bill?

Bill: Mine's a pint of lager.

Etc.

So:

What's yours? = What drink do you wish to have?

Mine's a ... = I'd like a ...

'Horsey' refers to a certain type of upper-class person who owns and rides horses

They spend a lot of time outdoors with their horses and the women often wear a headscarf as a protection against the weather.

Below is a photograph of a young H.M. Queen Elizabeth looking at horses whilst wearing a headscarf and gloves. (Edited to add 'gloves')

Solution 2:

chasly from UK's answer is correct, I think what the author is really trying to get across is that they're posh, or at least dress that way. A gin and tonic is a popular enough drink with all classes of England now, but if you look like your drink of choice is a G&T then you are definitely not working class.

The picture included in the discussion of the word horsey is of the Queen, I think that's a great choice of picture. It can also mean is interested in horses generally, but I don't think it does in this context.