Found the following hamletworks.org entries referring to line 51

View Commentary Note for 46
46 Bar. Last night of all,1.1.35

View Commentary Note for 51-52
51 {Enter Ghost.}1.1.40
51-52 Mar. Peace, breake thee of, <Enter the Ghost.> | looke where it comes againe.

View Immaterial Textual Note for 51-52
51 {Enter Ghost.}1.1.40
51-52 Mar. Peace, breake thee of, <Enter the Ghost.> | looke where it comes againe.

View Material Textual Note for 51-52
51 {Enter Ghost.}1.1.40
51-52 Mar. Peace, breake thee of, <Enter the Ghost.> | looke where it comes againe.

View Commentary Note for 76
76 Such was the very Armor he had on,1.1.60