The first edition to contain manuscript variations, Stephanus’ of 1550, displayed them in the margin. That is to say, he took the same option as that found in members of Family 1 [i.e., presents alternative readings as marginalia]. The reading in the text and marginal reading are linked by arabic numerals, and the witnesses are distinguished by each receiving a Greek number. . . . Stephanus did not invent the system, which is already found in editions by the Italian humanist Politian at the end of the fifteenth century.

D. C. Parker, An Introduction to the New Testament Manuscripts and Their Texts, 193.