Rainier, The date/mfg code starting with K 1 0 would be down in the void below the trim ring, next to the valve stem hole. I have never seen a set not stamped.
The hard to find 5/8"x1" clearance hole wheels are a partial production year wheel. As best we could determine at
www.nastyz28.com the changeover to 13/16"x1" hole wheels occured around June 1, 1970
While your price may (or may not) seem stiff to some, if you have a show quality early to mid year 70 Z-28 and are missing these wheels, its a dead give away to lack of originality.......
__________________
Chuck Sharin
[email protected]
Auburn,WA (30 miles South of Seattle)
70 Camaro R/S Z-28, L-78, R/S SS
69 Camaro COPO "recreation"