MikrotTik RouterBoard 750GL & RouterBoard 450

I cleaned up the garage and found in a box a white plastic unused MikrotTik 
RouterBoard 750GL & a used black all steel MikroTik RouterBoard 450 (which 
is built like the Tonka trucks we used to play with when we were kids).

They don't have power supplies but they say on them they will take anywhere 
between 8 to 30 VDC (and both have a dual Ethernet/POE port anyway). I 
opened up the black Routerboard 450 (it had four solid screws) because there 
was no model number sticker which even has a JTAG port on the motherboard, 
along with a second power supply port inside (and an RS-232-looking-like 
connector for a "serial console"). They used to build things well in the 
olden days I guess.

Each has 5 RJ45 ports, four of which are labeled Eth2, Eth3, Eth4, & Eth5.
What can I do with them that would make them useful to me?

Since they're not Wi-Fi, are they useful as dumb switches, for example?
(they didn't come with a power supply so that will be a minor issue)

What use would you find for these spare parts MikroTik routerboard boxes?