1 9 0 5 – 1 9 7 5 ▁▁ ▁Early ▁models ▁market ed ▁by ▁Con way ▁Stewart ▁were ▁s our ced ▁from ▁other ▁manufact ur ers , ▁were ▁made ▁of ▁hard ▁rub ber ▁and ▁were ▁ind ist ingu ish able ▁from ▁many ▁other ▁pens ▁available ▁at ▁that ▁time . ▁ ▁By ▁the ▁mid - 1 9 2 0 s , ▁the ▁company ▁was ▁establish ing ▁its ▁own ▁design ▁style , ▁helped ▁by ▁the ▁use ▁of ▁colour ful ▁cell ul oid ▁and ▁case in ▁pl ast ics . ▁ ▁Con way ▁Stewart ' s ▁model ▁design ation ▁is ▁a ▁combination ▁of ▁names ▁and ▁numbers . ▁ ▁Import ant ▁named ▁models ▁with ▁approximate ▁age ▁ranges ▁include : ▁▁▁ 1 9 2 0 s ▁– ▁ 1 9 6 0 s : ▁D ink ie ▁( 5 4 0 – 5 5 0 ) ▁▁ 1 9 3 0 s ▁– ▁ 1 9 4 0 s : ▁D uro ▁( vari ous ▁numbers ), ▁D and ie ▁( 7 2 0 , ▁ 7 2 8 ), ▁S cribe ▁( 3 3 6 ), ▁International ▁( 3 5 6 ), ▁Universal ▁( 4 7 0 , ▁ 4 7 9 ) ▁ ▁During ▁the ▁ 1 9 4 0 s , ▁model ▁names ▁were ▁dropped ▁for ▁all ▁product ▁lines ▁apart ▁from ▁the ▁D ink ie . ▁ ▁The ▁model ▁number ing ▁is ▁not ▁chron ological ▁and ▁the ▁same ▁pen ▁may ▁appear ▁with ▁a ▁different ▁numbers ▁depending ▁on ▁whether ▁it ▁was ▁sold ▁in ▁Britain ▁or