Not possible to ODIN older stock ROMs?

I swear I had dome this before, but here's my story.
Currently on Android 6.0.1 N910PVPU4DPE1 firmware
Flashed TWRP recovery yesterday and then did the following:

Selected "Wipe" in TWRP
Selected "Advanced Wipe"
Chose Dalvik/ART Cache, System, Data, Internal Storage and Cache
From TWRP main menu, selected "Reboot" and then selected "Download"
With phone in Download Mode, launched ODIN and then selected AP and loaded the N910PVPU3BOF5_N910PSPT3BOF5_N910PVPU3BOF5_HOME.tar .md5

The flash immediately fails with the following showing from ODIN

<ID:0/004> Added!!
<OSM> Enter CS for MD5..
<OSM> Check MD5.. Do not unplug the cable..
<OSM> Please wait..
<OSM> N910PVPU3BOF5_N910PSPT3BOF5_N910PVPU3BOF5_HOME.tar .md5 is valid.
<OSM> Checking MD5 finished Sucessfully..
<OSM> Leave CS..
<ID:0/004> Odin engine v(ID:3.1005)..
<ID:0/004> File analysis..
<ID:0/004> SetupConnection..
<ID:0/004> Initialzation..
<ID:0/004> Get PIT for mapping..
<ID:0/004> Firmware update start..
<ID:0/004> SingleDownload.
<ID:0/004> aboot.mbn
<ID:0/004> NAND Write Start!!
<ID:0/004> sbl1.mbn
<ID:0/004> rpm.mbn
<ID:0/004> FAIL! (Auth)
<ID:0/004>
<ID:0/004> Complete(Write) operation failed.
<OSM> All threads completed. (succeed 0 / failed 1)

Is it possible to flash an older stock Android version, or am I just beating a dead horse?

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