Lots of torx screws to undo to open it up.
On the edge of the base unit opposite the edge that has the ports, there is a rectangular cut out. It is either plugged with a plastic insert, accommodates the business end of a floppy drive, or is missing both and just open to the air, allowing you to peer inside. In the first or third cases, you lack the floppy drive. In the first and second cases, you may have a hard drive, although it may or may not still work. They used a lot of Prairie-Tek hard drives early on and the things were failure prone.
Only 20, 40, 60, and 80 MB hard drives work in the 125, according to Outbound tech support back in the day. I've never tested other drives in it. The Connor CP2064 and CP2084 work well, IIRC. I could be misremembering that. It seems like there was a Maxtor drive too. Anyway, they're all 2.5", IDE drives -- yes, IDE, not SCSI.
And really, if you have an opportunity, please ask the previous owner about the docking card. He probably never had one, but since he was a dealer, he is more likely than average to have had one, and he might have a lead to one. I really, really, really want a docking card. It's my holy grail of unobtained old Mac stuff.
If you lack a floppy drive, but have a working hard drive, and assuming you have an older Mac with serial ports, there is a work around for not having a floppy drive.
Open the unit up and if there is not a Silicon Disk installed, install some SIMMs in the four slots for the purpose (125 has 9 SIMM sockets, four for Silicon Disk, four for system RAM (4MB Max.) plus one more for the ROM SIMM).
Close her up and boot from the hard drive. Copy your system folder to the Silicon Disk. Set AppleTalk to communicate through one of the serial ports and connect a PhoneNet or LocalTalk network to another Mac. On that Mac, insert a floppy disk and then under System 7 or later share the floppy disk (pretty sure this worked back when). Back on the 125 use AppleShare in System 6 or 7 to mount the shared volume and then install whatever you need to.
If you want to change the OS on the hard drive, you can use the above method, just make sure you don't lose power (use battery & AC adapter) to the Silicon Drive while the hard drive is in the transition state.
The 125 does not work with systems past 7.0.1, I think. I'm pretty sure it does not work with 7.1.
In any event, when you install a new system from Apple disks, you need to run an Outbound installer utility. This utility makes some minor modifications to the OS and adds a bunch of Desk Accessories or Control Panels which are specific to the Outbound. It also detects the Outbound's hardware configuration and writes appropriate code to a pair of 64Kbit EEPROMs inside the machine.
On the edge of the base unit opposite the edge that has the ports, there is a rectangular cut out. It is either plugged with a plastic insert, accommodates the business end of a floppy drive, or is missing both and just open to the air, allowing you to peer inside. In the first or third cases, you lack the floppy drive. In the first and second cases, you may have a hard drive, although it may or may not still work. They used a lot of Prairie-Tek hard drives early on and the things were failure prone.
Only 20, 40, 60, and 80 MB hard drives work in the 125, according to Outbound tech support back in the day. I've never tested other drives in it. The Connor CP2064 and CP2084 work well, IIRC. I could be misremembering that. It seems like there was a Maxtor drive too. Anyway, they're all 2.5", IDE drives -- yes, IDE, not SCSI.
And really, if you have an opportunity, please ask the previous owner about the docking card. He probably never had one, but since he was a dealer, he is more likely than average to have had one, and he might have a lead to one. I really, really, really want a docking card. It's my holy grail of unobtained old Mac stuff.
If you lack a floppy drive, but have a working hard drive, and assuming you have an older Mac with serial ports, there is a work around for not having a floppy drive.
Open the unit up and if there is not a Silicon Disk installed, install some SIMMs in the four slots for the purpose (125 has 9 SIMM sockets, four for Silicon Disk, four for system RAM (4MB Max.) plus one more for the ROM SIMM).
Close her up and boot from the hard drive. Copy your system folder to the Silicon Disk. Set AppleTalk to communicate through one of the serial ports and connect a PhoneNet or LocalTalk network to another Mac. On that Mac, insert a floppy disk and then under System 7 or later share the floppy disk (pretty sure this worked back when). Back on the 125 use AppleShare in System 6 or 7 to mount the shared volume and then install whatever you need to.
If you want to change the OS on the hard drive, you can use the above method, just make sure you don't lose power (use battery & AC adapter) to the Silicon Drive while the hard drive is in the transition state.
The 125 does not work with systems past 7.0.1, I think. I'm pretty sure it does not work with 7.1.
In any event, when you install a new system from Apple disks, you need to run an Outbound installer utility. This utility makes some minor modifications to the OS and adds a bunch of Desk Accessories or Control Panels which are specific to the Outbound. It also detects the Outbound's hardware configuration and writes appropriate code to a pair of 64Kbit EEPROMs inside the machine.