Is there a method from examining the block chain to determine how many blocks are being allocated to POS and how many to POW over a certain time period?

short of examining over a certain time period are POS & POW blocks identified differently?

I ask because I have a need to sum the total number of block allocate to POW over certain time periods and if this can be done will the 'method' hold true for all coins that have both POW & POS?

thanks in advance.