After also signing the society's 150th-anniversary book, the Queen was gifted a copy of the book, to which she said, "Oh that’s very kind, thank you."
"Is that the same as this one?" she asked, pointing at the book she had just signed. A member pointed to the book she had just signed and told her, "apart from that it’s not signed."
The Queen replied: "Oh well, never mind."
The Queen was also shown a book that had been donated by her philatelist grandfather, King George V, with his signature in the front. Told that it was still one of their 'go-to' books on the Victorian period, she said: "Really, how fascinating. Is it still up to date?"
"Well only until 1900!" She was told, which left her amused. "Well it was a good one, then," she laughed.
After a welcome from Alderman William Russell, The Rt.Hon. the Lord Mayor of the City of London, the Queen was introduced to senior staff by the President of the Royal Philatelic Society.
Discussing the society's move to the building, the 93-year-old said: "That must have been quite a business, I should think, wasn't it? Quite stressful. I hope you are enjoying the place."
The Queen was shown letters written by her grandfather who was a noteworthy stamp collector.
"He was a great collector," Her Majesty said. Pointing to one of his letters, she added: "It's great to be able to show it."
The Queen was also shown stamps depicting monarchs - including herself, Queen Victoria, King Edward VII, King George V and King George VI.
"Oh yes, I remember that one," she remarked when she recognised her Coronation stamp. Spotting her grandfather again, she added: "George V, he was always so interested."