Oliver Cowdery initially repeated the preposition of before the conjunct the Lamb, but then he deleted the of (with no apparent change in the level of ink flow for the crossout). The lack of repeated of does not necessarily mean that God is indistinguishable from the Lamb. The humble follower of one is a follower of the other, which means that the repeated of can be avoided because of the close association between God and his Son. A similar lack of repeated of in referring to God and the Lamb occurs elsewhere in the text:
In other words, the text does not read “the sword of the justice of the eternal God and of Jesus Christ which is the Lamb of God”. The unity of the Father and the Son is thus supported by the lack of the repeated of in both these passages. Most likely, Oliver’s correction here in Helaman 6:5 was in accord with the reading of the original manuscript (not extant here), especially since otherwise there would have been no strong motivation for removing the repeated of.
Summary: Accept in Helaman 6:5 Oliver Cowdery’s corrected text in the printer’s manuscript without the repeated of before the Lamb (“to be the humble followers of God and the Lamb”).