The 69 production year started in August 1968 if I remember right at 500001. This sequence was used for both assembly plants and since they were assigned centrally 500001 could have been assembled by Chevrolet at Norwood, while 500002 could have been assembled by GMAD at Van Nuys - Los Angeles. So no duplicates there.
In August of 1969 the central office reset the number to 100000 at Norwood for Chevrolet assembly to account for the extended 69 run, and GMAD Van Nuys - Los Angeles retooled all its lines for the 70 model year on schedule except Camaro. GMAD had not produced any vehicles in May due to a full strike, and less than 1000 Camaro's in June and under 150 in July. No additional Camaro's were assembled at GMAD Van Nuys - Los Angeles until the new 70 body was tooled up. By the time extended production ended in November 1969 Norwood had only produced approx 42,803 vehicles under the 100000 sequence.
So to answer your question. No duplicates would exist unless the tag is a fake or a fluke.