[Andrew Musau]

tostring _merge, gen(me)
destring me, replace
gen keepit=0
replace keepit=1 if me==1
replace keepit=2 if me ==3
drop if keepit<1

This will work, but is not necessary.

merge 1:1 identifier0 using "location", keep(master match)

[Sarah Holts]

Thanks for your help!!