This is a set of 4 NOS GM center caps for the turbine wheels on a Monte Carlo.  I have seen some of these advertised as 1973 - 1975 and the same part number for 1976 - 1977.  In looking at pictures of the different years it appears these were used on 1973 - 1977 Monte Carlo with turbine wheel.  The boxes are not pretty but the caps are mint.