Question: What was the nationality of the designer or developed Spacemaster with Kevin Barrett?

Context paragraphs:
Barrett Firearms Manufacturing: Barrett Firearms Manufacturing is an American manufacturer of firearms and ammunition located in the unincorporated town of Christiana, Tennessee.  It was founded in 1982 by Ronnie G. Barrett for the single purpose of building semi-automatic rifles chambered for the powerful .50 BMG (12.7×99mm NATO) ammunition, originally developed for and used in M2 Browning machine guns.  Barrett began his work in the early 1980s and the first working rifles were available in 1982, hence the designation M82.  Barrett designed every single part of the weapon personally and then went on to market the weapon and mass-produce it out of his own pocket.  He continued to develop his rifle through the 1980s, and developed the improved M82A1 rifle by 1986.

Kevin Barrett (cricketer): Kevin Barrett (born 16 November 1975) was a Welsh cricketer.  He was a left-handed batsman and right-arm medium-pace bowler who played for Devon.  He was born in Swansea.

Kevin Ayers: Kevin Ayers (16 August 1944 – 18 February 2013) was an English singer-songwriter who was a major influential force in the English psychedelic movement.  Ayers was a founding member of the pioneering psychedelic band Soft Machine in the mid-1960s, and was closely associated with the Canterbury scene.  He recorded a series of albums as a solo artist and over the years worked with Brian Eno, Syd Barrett, Bridget St John, John Cale, Elton John, Robert Wyatt, Andy Summers, Mike Oldfield, Nico and Ollie Halsall, among others.  After living for many years in Deià, Majorca, he returned to the United Kingdom in the mid-1990s before moving to the south of France.  His last album was "The Unfairground", recorded in New York City, Tucson, and London in 2006.  The British rock journalist Nick Kent wrote: "Kevin Ayers and Syd Barrett were the two most important people in British pop music.  Everything that came after came from them."

Terry K. Amthor: Terry K. Amthor (born October 18, 1958) is an American game designer who has worked primarily on role-playing games, and as a fantasy author.

Kevin Barrett (game designer): Kevin Barrett is a game designer who has worked primarily on role-playing games.

Mage Knight: Mage Knight is a miniatures wargame using collectible figures, created by WizKids, Inc, and is the earliest example of what is now known as a Collectible Miniatures Game.  The game was designed by founder Jordan Weisman along with Kevin Barrett.  The game is the first to use WizKids' Clix system, combining roleplaying and wargaming elements with aspects of collectible card games.  "Mage Knight" achieved success after it was introduced in 2000.  WizKids announced in October 2010 that "Mage Knight" was being relaunched with a board game, card game, and role-playing game.

Spacemaster: Space Master is a science fiction role-playing game produced by Iron Crown Enterprises, written by Kevin Barrett, developed by Kevin Barrett and Terry K. Amthor.

Bob Marley and the Wailers: Bob Marley and the Wailers were a Jamaican reggae band led by Bob Marley which developed from the earlier ska vocal group, the Wailers, created by Marley with Peter Tosh and Bunny Wailer in 1963.  By late 1963 singers Junior Braithwaite, Beverley Kelso, and Cherry Smith had joined the Wailers.  By the early 1970s, Marley and Bunny Wailer had learned to play some instruments and brothers Aston "Family Man" Barrett (bass) and Carlton Barrett (drums), had joined the band.  After Bunny Wailer and Peter Tosh left the band in 1974, Marley began touring with new band members.  His new backing band included the Barrett brothers, Junior Marvin and Al Anderson on lead guitar, Tyrone Downie and Earl "Wya" Lindo on keyboards, and Alvin "Seeco" Patterson on percussion.  The "I Threes", consisting of Judy Mowatt, Marcia Griffiths, and Marley's wife, Rita, provided backing vocals.

Kevin Barrett (rugby union): Kevin Barrett (born 6 July 1980) and attended Stonyhurst College.  He is a rugby union player for Exeter Chiefs in the Aviva Premiership.  He plays as a scrum-half.  On 22 March 2011, Barrett announced his resignation from the Exeter Chiefs for the 2011/2012 season.  He was previously with fellow Aviva Premiership side Saracens.

Kevin Barrett (footballer): Kevin Barrett (born 10 July 1915) is a former Australian rules footballer who played with Collingwood and South Melbourne in the Victorian Football League (VFL).

Supporting paragraphs: Spacemaster Terry K. Amthor
Answer: American