No real secret but just for documentation purposes : Marzocchi built different early Bomber crowns. Here for example a classic Bomber Z1 (left, 298gr) from 1997 and a Bomber Z2 BAM (right, 226gr) from 1999. Look at it : hey have different heigths (10mm).
I believe this happend because of optimizing. As you might know : the BAM’s where made out of a special aluminium (BAM : Bomber Aerospace Material), got a more milled brace and smaler stanchion caps, just to reduce some weight.