So, I'm the guy with a GDS-2074A (actually rebranded as a Isotech (RS) IDS-2074A). Sorry for the delay in replying, currently on paternity after the birth of my second child!
Plugging in the device to my linux box using USB I get most of what you're after:
[2604763.960679] usb 3-4: new full-speed USB device number 16 using xhci_hcd
[2604764.113082] usb 3-4: not running at top speed; connect to a high speed hub
[2604764.128062] usb 3-4: New USB device found, idVendor=2184, idProduct=0014, bcdDevice= 2.26
[2604764.128066] usb 3-4: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[2604764.128070] usb 3-4: Product: IDS-2074A
[2604764.128072] usb 3-4: Manufacturer: RS
[2604764.128075] usb 3-4: SerialNumber: 524D093G1
[2604764.135403] cdc_acm 3-4:2.0: ttyACM0: USB ACM device
Hopefully the data you need is in there?
Connecting via RS232 serial, and running the SCPI *IDN? command I get
RS,IDS-2074A,524D093G1,V1.30
Probably RS components, device, serial, and firmware version which is currently 1.30
On reboot, I don't see anything in the RS232 output. Is there some special baud for the message you need? I've tried 19200, 57600, and 115200.
Otherwise, do I have to find a debug header inside the device?