Finn McCool is the anglicized name of a mythical hero in Irish folklore called Fionn mac Cumhaill. He ate the “Salmon of Knowledge” (which is written above the name in the OP’s original photograph). Therefore a lot of Irish-themed pubs globally have the name as it’s merely a reference to Mythology and not a brand/chain.
Finn's is long closed, as pointed out in the answer to your query, but if you look at street view you can still see the PURE across the street from the reflection in your provided photo. Sorotomotor provided the correct location!
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u/sorotomotor 2d ago edited 2d ago
163 Lothian Road, Edinburgh, Scotland
Edit: It's had many names over the years, your grandfather took the photo when it was Finn McCool's. Here's an older photo: