ERROR: Unsupported platform srx210h for 12.1X47 and higher
This is the error that you will get if you try and install 12.1X47 on a Juniper SRX 210H (or 100B, 100H or any "first gen" srx).
"Note: Upgrading to Junos OS Release 12.1X47-D10 or later is not supported on the J Series devices or on the low-memory versions of the SRX100 and SRX200 lines."
I thought maybe it would just be the base memory devices e.g SRX100B or SRX210B but it looks like any SRX device with 512MB or 1GB ram are not supported.
This is a shame as for example the SRX110H devices weren't that old and supported removable/upgradable CF cards. Even the SRX240B2 is not supported! You need 2GB of ram.
The ASA5505 is good example of a device designed to last. Pity I like JunOS so much!
I have a couple of SRX240Hs, these allow you to upgrade the ram (standard DDR2), so I wonder if an upgraded 240H will work.