Some dropouts also contained a semi-circular bolt holding the rear derailleur. If this is the case then there is no problem.

As long as the wheel runs straight and the drop outs are centered then you have nothing to worry about. To check if the drop outs are centered on the frame - fit the wheel so that it is straight in relation to the seat tube, take the bike out for a ride, ride for a few seconds with no hands. If the bike doesn't drift off to the side then it is centered.