In 1956 this group of Martinez officers posed with two 1956 Pontiac 4 door sedans (not hard tops). It is very likely that these were both the Chieftain model, the baseline offering.
Pontiac Chieftain 4 doors seem to sell at under $15,000 in good condition and down to sub-$2k for rougher examples.
- $10k example: https://www.hemmings.com/classifieds/cars-for-sale/pontiac/chieftain/2306165.html
- $2k example: https://classiccars.com/listings/view/1238298/1956-pontiac-4-dr-sedan-for-sale-in-crookston-minnesota-56716
