Update:

StreetPilot 26x0 uses a different method to dump which combines elements of the 'Packet Data' method described by juergenss and the straightforward/direct 'Region Dump' described by Kanopus which works for me with SP27x0.

In 'GARMIN Interface' tab, this is the procedure for 26x0 StreetPilots:
1. Press Open in Port field.
2. Enter desired region [use hex] in Region Dump field.
3. Press Start. [Dump doesn't start as with SP27x0].
4. Go to Packet Header field, enter '60' in Packet ID [HEX] window.
5. Check Send Data.
6. In Data bytes to send [DEC] window enter '2'.
7. In Window 1 of Data to Send [HEX] enter the required region again.
8. Press 'Send' and the Region memory dump will start to a DUMP folder in the same directory as GPSDaemon.exe.

[Only registered and activated users can see links. ]

26x0 doesn't have any on-board mapping other than the basemap with maximum 16 MB allocated to region 3 same as 27x0. Attempting to dump regions 49 [hex 31] or 50 [hex 32] curiously gets regions 16 [hex 10] & 15 [hex 0F] instead. Region 14 [0E] for fw_all dumps successfully but has only 4MB maximum available, much less than 27x0's 10MB.

Unfortunately no usable data in 2610's region 16 to reconstruct logo.bin. Full of 2.87MB of empty FF's. Any clues from the NSEs or other experienced ppl, please?

I haven't been able to get SPc320 to dump any region at all. So do the old hands have ideas on that too?