 The Sovereign was one of the last calculators produced during Sinclair 's foray into the calculator market that had started with the Sinclair Executive in September 1972 . The Executive had retailed for GB £ 80 when introduced , but in little over a year it was possible to purchase a Sinclair calculator for GB £ 20 and by November of 1976 a model was available for GB £ 4 @.@ 95 . Cheaper calculators with liquid @-@ crystal displays instead of light @-@ emitting diodes were becoming more popular , and had much longer battery lives of months or years . Such calculators were available for well under GB £ 10 , with all the functionality of the more expensive models . The impossibility of selling " simple " calculators profitibly led Sinclair to introduce models such as the Cambridge Scientific , introduced in August 1975 at a price of GB £ 29 @.@ 95 . 
 The Sovereign was one of the last calculators produced during Sinclair <a href='null_genetive' title='1'><mark>'s</mark></a>foray into the calculator market <a href='null_relcl' title='2'><mark>that</mark></a><a href='been_done' title='3'><mark>had</mark></a> started with the Sinclair Executive in September 1972 . The Executive <a href='been_done' title='4'><mark>had</mark></a> retailed for GB £ 80 when introduced , but in little over a year it was possible to purchase a Sinclair calculator for GB £ 20 and by November of 1976 a model was available for GB £ 4 @.@ 95 . Cheaper calculators with liquid @-@ crystal displays instead of light @-@ emitting diodes <a href='uninflect' title='5'><mark>were</mark></a> becoming more popular , and had much longer battery lives of months or years . Such calculators <a href='uninflect' title='6'><mark>were</mark></a> available for well under GB £ 10 , with all the functionality of the more expensive models . The impossibility of selling " simple " calculators profitibly led Sinclair to introduce models such as the Cambridge Scientific , introduced in August 1975 at a price of GB £ 29 @.@ 95 . 
The Sovereign was one of the last calculators produced durin Sinclair  foray into da calculator market done started with the Sinclair Executive in September 1972 . The Executive done retailed fir GB £ 80 when introduced , but in lil ova a year it was possible to purchase a Sinclair calculator fir GB £ 20 and by November of 1976 a model was available for GB £ 4 @.@ 95 . Cheaper calculators wid liquid @-@ crystal displays instead of light @-@ emitting diodes was becoming more popular , and had much longer battery lives of months or yrs . Such calculators was available for well under GB £ 10 , wwidall tdafunctionality of the more expensive models . The impossibility of selling " simple " calculators profitibly led Sinclair to introduce models such as the Cambridge Scientific , introduced in August 1975 at a price of GB £ 29 @.@ 95 .