Bas, as Malmojoe & Jimmock have mentioned the Z1's & early Z1A's were without lip and only had a shorter pad [65mm long].
I think, to prevent theft, and over-stamping about #27700 Kawasaki tried this...
extending the pad to 80mm snd giving the overall surface of the pad a lip.
Also, for a short period a checkered surface. The checkered surface must not have been successful as, I think, certain number stampings interfered with the surface and caused pieced of alloy to fall out!
I have found this only went for a few units [approx 400 to 1000 units], after which it changed to the original large font then to the last font which is smaller and slightly italic. It also gained an extra digit along the way. I have seen anomalies around this # 27700 sequence, however, as they were so good, I had to accept them or embarrass the owner.
To my knowledge, the Z1B had the 80mm pad with lip and had the six digit small slightly italic font
RegardZ.