It is more than a century after first-class passengers on board the ill-fated RMS Titanic ate grilled mutton chops and custard pudding in an elaborate dining room. And now the ship's last luncheon menu is expected to fetch up to £46,000 ($70,000) in an online auction. The menu is one of three items found on the first lifeboat that left the sinking vessel.

"What makes these relics so collectable is that there is so few of them. Almost everything and almost all the people went down with the ship. So anybody who was rescued could really only take what they had stuffed into their pockets. And for someone to think of having a menu from their last lunch aboard the Titanic, and either intentionally or coincidentally put it into their pocket and take with, them is unusual. Also because paper is so fragile to begin with that anything of that nature is going to be very hard to preserve," said David Lowenherz, owner of Lion Heart Autographs.

Yesterday (1 September 2015) marked 30 years since the wreckage of the ship, which had been called unsinkable before its ill-fated maiden voyage, was discovered on the ocean floor by a team of researchers. The luncheon menu will be auctioned along with a letter written by one of the ship's survivors and a ticket from the Titanic's Turkish baths weighing chair, used to measure a person's weight.

"There have been at least two or three menus from the last menu aboard the Titanic – that's when this menu was issued. Lunch for April twelfth – I'm sorry, lunch for April fourteenth, 1912. And one of them was sold, I think, maybe about three years ago at an auction in England for I think something in the order of $120,000. They are very, very rare," Lowenherz explained.

"The weighing ticket, even though it's very small and appears to be quite insignificant, there are also only about three or four examples of that known. Again, it is paper, didn't survive and so on. And any letter written by one passenger – from one rescued passenger to another rescued passenger, contemporaneous to the event – is also very, very rare."

The artefacts are all associated with passengers who survived the sinking of the Titanic on Lifeboat No 1. Nicknamed the 'money boat', it became controversial amid accusations that wealthy passengers bribed crew members to row away from the sinking ship before the lifeboat was full. About 1,500 people died during the Titanic's sinking, with third-class passengers suffering the greatest losses. The menu was saved by first-class passenger Abraham Lincoln Salomon and was signed on the back by Isaac Gerald Frauenthal, a passenger from New York who had likely eaten lunch with Salomon that day.

Stamped with a date of 14 April 1912 and the White Star Line logo, the menu also included corned beef; mashed, fried and baked jacket potatoes; a buffet of fish, ham and beef; an apple meringue pastry; and a selection of eight cheeses. Lowenherz expects the buyer to be someone who is passionate about Titanic history.

"I think the typical buyer for something like this is someone who is very passionate about the Titanic and its history. In doing research for these three pieces I found that there are such buyers and collectors throughout the world. Not just in the United States or in England or Ireland, as one would think. But as far as China, the Mideast, Australia, it is a story that grips people's imaginations regardless of where they are."

The online auction will take place on 30 September at Invaluable and eBay.