Would they have used the bolts with the star washers or would they have used the bolts similar to the fender bolts with the serrated washer with the double tick marks? I believe there is mix use during this timeframe
Yes it depended on which bolts your discussing. Both star and "flat" or round washers were used in the Jan-March period
Challenge for battery tray hardware is that normally there is a battery mounted and in the way to see or if the car is disassembled the battery tray is removed
This leaves us with the majority of pictures showing the lower two bolt heads that were installed from the wheel well side of things
It appears from pictures of unrestored cars between the 6R16000's into the 6R190000's that the change from star to round washers took place in the early 6R190000 period
From the identified time period and plant Clock wise from top left 6R167xxx Star - 6R172xxx Star - 6R199xxx Round -6R190xxx Star
Center 6R190xxx Round