I looked up #8327 in various on-line OREG/ORER's and found:
This series was not there in 1891
In series 8267-~8999 listed as "Palace" with no indication that they were double-deck in 1893-1894-1895
In sub-series 8267-8681 listed as double-deck as part of series 8267-8965 listed as "Stable" in 1897-1905.
1909-1911 are similar designated class R
class SB in 1913, but after 1905 it doesn't really differentiate between single & double deck cars.
Then I got tired of looking!
My take-away here is that these double-deck cars with roof hatches were built as single-deck Palace cars with roof hatched for feeding etc in about 1892.
Some time around 1896 they became "stable" cars, feeding was discontinued, some were rebuilt as double-deck cars, but the roof hatches were not removed.
They then lasted into the teens.
What do any of you think? - Tom E.