The hoard, which includes silver pennies dating back to the 10th and 11th centuries, was discovered by Walter Hanks in Llandwrog in March.
National Museum Wales said some of the coins were made under the ruler Sihtric Anlafsson and were a type rarely found on the British mainland.
It said they were likely to have been hidden or lost between 1020 and 1030.
Dr Mark Redknap, of the department of history and archaeology at National Museum Wales, said the mixed nature of the collection showed bullion played an active role in the 11th Century economy and gave an idea of the wealth of Gwynedd at the time.
The museum now hopes to buy the coins and put them on display.

The New York-based singer won the award for her Orchestre Philharmonique du Luxembourg collaboration, Sings.
"I want to dedicate this Grammy to all the traditional musicians in Africa, in my country, to all the young generation," Kidjo said.
Her album beat one by Malawi's Zomba Prison Project and South Africa's Ladysmith Black Mambazo.
Kidjo, one of Africa's most prominent musicians, has now won the award for the second consecutive year.
The album merges African song writing and rhythms with European classical instrumentation, a fusion on which Kidjo has repeatedly experimented.
Kidjo described the album as an artistic challenge as traditional African bands follow the lead of the soloist much more closely, unlike Western orchestras that generally play off refined scores.
The singer, who has worked for a long time with Philip Glass, a leading US composer, said Africa was on the rise.
"Africa is positive, Africa is joyful," she said after collecting the award.
The 55-year-old singer added that she has been fighting for a positive image of Africa for a long time and believed music could connect the world and served as a tool for peace.
She later told the BBC: "I have to continue to working...  to open the way for many artists from Africa to come."
African-American rapper Kendrick Lamar won the most prizes on the night with five awards.
The 29-year-old performed The Blacker The Berry, walking on stage as part of a chain gang from inside a prison, before transitioning to Alright, in front of a huge bonfire and African dancers.
His performance ended with the unveiling of a new track with Lamar in front of a map of the African continent and the word "Compton" - his hometown in California - written on it.

Boro are unbeaten in their last seven matches and are two points clear of second-placed Burnley, who drew 1-1 with Karanka's team on Tuesday.
"We are top of the table because we have an amazing squad and we have an amazing club," Karanka told BBC Tees.
"We are in a privileged position and we showed everyone we are a good team."
He added: "If we are at the top of the table at this point, it is no coincidence.
"We can say that we've lost two points, but I prefer to keep calm with the performance and with the players."
Jordan Rhodes gave Boro the lead with 20 minutes left to play against Burnley, but Michael Keane's 92nd-minute equaliser rescued a point for the Clarets.
"The way we were playing it was difficult to lose, but we played really well and everybody could feel at home and feel the difference between us and Burnley," Karanka said.
"We have a lot of different ways to get the ball into the box and they have just one: long balls."
Middlesbrough face Ipswich and Birmingham City before they meet promotion-chasing Brighton at the Riverside on the final day of the season.
"At home we are a really confident team and we have won the last three games there," Karanka said.
"We need the supporters' help because we're going to need everything at this point of the season, where every point is gold."
Viking coins and ingots found by a metal detectorist in Gwynedd have been declared treasure by a coroner.
[NEXT_CONCEPT]
Benin's Angelique Kidjo has won the best world music album of the year at this year's Grammys in Los Angeles.
[NEXT_CONCEPT]
Middlesbrough head coach Aitor Karanka says his side fully deserve to be top of the Championship table with three games left to play.