I agree with Pat's and Serge's assessment of the maker marks, they are the only "variants" that I have ever been comfortable with or seen on daggers I KNOW to have been period, the type with the smaller '&'. I have owned others with different maker marks including the open-hammer version which were very convincing, perhaps even period, but the anomalies always bothered me personally and are difficult to explain away.
But I think the dagger should also be viewed in its entirety. Early Packs are very distinctive, the scabbard fittings, shape & screw position, grip shape, motto style, inscription and maker mark all provide the signs, not to mention the hidden features like tang forge markings and crossguard caster marks. Besides the inscription and maker mark, the motto is not typical Pack, the scabbard fittings are also not typical, as is the grip shape.
Pack Rohms are a minefield, a ton of fakes, apparently the best of which were made by Attwood which are very difficult to identify. I think Zorro called this one...
Red
