▁the ▁open ▁market ▁began ▁in ▁Europe ▁and ▁Australia . ▁ ▁As ▁the ▁Bell ▁System ▁did ▁not ▁permit ▁the ▁operation ▁of ▁third - party ▁equipment ▁on ▁their ▁network , ▁the ▁Eric of on ▁could ▁only ▁be ▁used ▁by ▁independent ▁tele phone ▁companies ▁in ▁the ▁United ▁States . ▁North ▁Electric ▁in ▁Gal ion , ▁Ohio , ▁manufact ured ▁the ▁Eric of on ▁for ▁the ▁North ▁American ▁independent ▁market . ▁ ▁Design ▁The ▁original ▁phone ▁was ▁produced ▁in ▁two ▁slightly ▁different ▁designs . ▁The ▁earliest ▁version ▁is ▁slightly ▁t aller , ▁with ▁the ▁ear pie ce ▁at ▁nearly ▁a ▁ 9 0 - deg ree ▁angle ▁to ▁the ▁base . ▁A ▁later ▁version ▁has ▁a ▁shorter ▁handle , ▁with ▁the ▁ear pie ce ▁ang led ▁slightly ▁down ward . ▁The ▁two ▁versions ▁are ▁referred ▁to ▁as ▁the ▁old ▁case ▁and ▁the ▁new ▁case . ▁The ▁old ▁case ▁was ▁m old ed ▁in ▁two ▁pieces , ▁while ▁the ▁new ▁case ▁was ▁m old ed ▁as ▁a ▁single ▁piece . ▁Both ▁versions ▁were ▁initially ▁produced ▁in ▁ 1 8 ▁colors . ▁They ▁used ▁the ▁four - pr ong ▁plug ▁common ▁in ▁the ▁United ▁States ▁at ▁the ▁time . ▁ ▁A ▁third ▁version , ▁the ▁model ▁ 7 0 0 , ▁was ▁produced ▁beginning ▁in ▁ 1 9 7 6 . ▁It ▁is ▁easily ▁distinguished ▁from ▁earlier ▁Eric of ons ▁by ▁its ▁squ ar ish ▁design , ▁as ▁well ▁as ▁changes ▁to ▁the ▁handle ▁and ▁plug . ▁ ▁Colors ▁When ▁it ▁was ▁introduced ▁on ▁the ▁U . S .