270010S Suits early Singer machines with a domed, narrow drop in bobbin case.
Singer Class 66K bobbin. For older Singer drop in Singer Machines.  
For EX Models: 288, 247, 360, 774, 935, 1022, 1280, 2210, 2517, 2735, 2950, 3270, 3343, 4325, 4610, 4622/22a, 4830, 5040, 5050, 5070, 5160, 5417,
5430, 5705, 5825, 5830, 5910, 6012, 6038, 6233, 7021, 8222, 8734, 9110, 9210, 9300, 9400, 9410, 9608, 9858, 57815, 57820, 57825, CG-500, CG-550,
CG-590, HD110 and SR models: 240, 250, 320, 340, 350, 400, 500, 700, 800, 1800, 2500, 3100, 3300, 4500, 5800, 6100, 6200, 6500, 6700, 8000, 9000,
9800, and other top drop-in bobbin machines. Also post 1990 models: 1030, 1080, 1090, 1130, 1230, 1240, 1260, 1530. Activa Series: 130, 140, 150,
155, 170E, 215, 230, 330, 380, 530, 630, 1008.