Amiga 1000 system boards

Any Amiga geeks out there? I picked up a pair of Amiga A1000 systems a couple of weeks ago. Both are Revision 6 boards (going by IC dates, one was likely built in October of '85, the other in January of '86). However, bigbookofamigahardware.com claims that rev. 6 boards had copper traces and the later rev A board were tin - but in this case the earlier of my two boards is tin (while the later one is indeed copper). Just wondering if I have a bit of an anomaly (and the above site's correct), of if the reality is that rev. 6 boards routinely appear in both copper and tin? s/n on the early system is 6000146, the later one is 1165109; I have no idea what production numbers were like (anyone?) but I'm assuming that there's some form of plant number involved in the leading digit(s). cheers Jules