There is a very different feeling to brake (clutch) fluid and engine oil on your fingers. If it was clutch fluid, expect to find the level has dropped in the master cylinder.
Flanges on primaries are rectangular with 4 bolts each. This was from a Ford BDR engine. Finish is lightly tarnished but would polish up well. Example photo attached.
+ve goes to the terminal on the starter motor that is switched by the solenoid to operate the starter. otherwise it would be running the whole time ! Same terminal connects onwards to the alternator output terminal.