;-) Okay, the red rectangle indicates the processor slot, so your card is probably an accelerator card with a built-in controller, which is almost certainly SCSI. The card in the black rectangle and the wire soldered to one leg of the chip on the mother board looks to be a Chip RAM expansion set-up, which would give you two megabytes of Chip RAM instead of the default one megabyte. Likely an earlier owner had this installed and sold it off separately, leaving the wire behind.
;-) And yes, the startup sequence is simply a text file called, appropriately enough, startup-sequence. When AmigaOS starts up, it looks for a file with this name, in a directory called “s,” at the root level of whichever drive you’re booting from.