Even if it is DNA, if it encodes the same proteins in the same way than the life here would a be very improbable event. Think in an alien alphabet looking like ours, but also making the same sounds and some common words and meanings with the similar looking symbols.

“Origin” in this case would be something in the very physically close and near term. Something that excludes the possibility of serious evolutionary change. Even relatively static species undergo mutations in the long term.

So if something is an exact match it is evident that they came from the same time and place (within some reasonable window). The origin would implicitly be Earth in the 1960s.