|Note_en=Advertising for the [[Parker 51]] model with ''[[Lustraloy]]'' cap, citing also the ''[[Signet]]'' version and the [[Aero-metric Ink System|Aero-metric]]. Mention also the [[Parker 21]] and some new ''[[Duo-fold]]''. | |Note_en=Advertising for the [[Parker 51]] model with ''[[Lustraloy]]'' cap, citing also the ''[[Signet]]'' version and the [[Aero-metric Ink System|Aero-metric]]. Mention also the [[Parker 21]] and some new ''[[Duo-fold]]''. |