12 week old golden Sex link pullet or roo?
If your feed store got the chicks from a hatchery then it is a pullet. The whole point of sex links is to produce chicks that can be sexed by down color. Female red/gold sex link chicks are reddish in color and males are white. The sex linkage works for one generation only.
Now if they got chicks from someone breeding sex link to sex link the answer could be different.