▁designs ▁and ▁the ▁t anks ▁produced ▁were ▁identified ▁by ▁General ▁Staff ▁specification , ▁tank ▁type , ▁the ▁mark ▁( e ither ▁of ▁type , ▁or ▁of ▁specific ▁model ), ▁a ▁service ▁name , ▁and ▁version . ▁ ▁For ▁example , ▁the ▁A 2 7 M ▁specification ▁for ▁a ▁cru iser ▁tank ▁entered ▁service ▁as ▁' T ank , ▁Cru iser , ▁Mark ▁VIII ' ▁( the ▁e ighth ▁cru iser ▁design ▁to ▁see ▁service ) ▁with ▁the ▁service ▁name ▁' C rom well ' ▁and ▁was ▁produced ▁in ▁eight ▁variants ▁- ▁C rom well ▁I ▁to ▁VIII . ▁A ▁related ▁design ▁but ▁with ▁a ▁different ▁engine ▁- ▁specification ▁A 2 7 L ▁ ▁- ▁was ▁the ▁' T ank , ▁Cru iser , ▁Mark ▁VIII ▁Cent aur ' ▁ ▁This ▁means ▁that ▁vehicles ▁may ▁be ▁referenced ▁in ▁part ▁or ▁whole ▁by ▁combination ▁of ▁those ▁elements . ▁ ▁Spec ification ▁Number ▁ ▁General ▁Staff ▁specification ▁was ▁a ▁reference ▁to ▁the ▁requirements ▁developed ▁by ▁the ▁Director ate ▁of ▁T ank ▁Design ▁e . g . ▁A 1 3 . ▁These ▁were ▁specific ations ▁for ▁which ▁new ▁t anks ▁were ▁to ▁be ▁designed . ▁ ▁Not ▁all ▁specific ations ▁led ▁to ▁vehicles ▁being ▁put ▁into ▁production . ▁More ▁than ▁one ▁design ▁could ▁be ▁drawn ▁up ▁to ▁a ▁single ▁specification ▁and ▁hence ▁more ▁than ▁one ▁tank ▁produced ▁to ▁the ▁same ▁specification . ▁If ▁the ▁vehicle ▁was ▁priv ately ▁developed ▁it ▁may ▁not ▁have ▁a ▁General ▁Staff ▁number ▁at ▁all . ▁ ▁A ▁significant ▁red es ign ▁could