Hello Brianh, 

OpenStreetMap is a database for current data. Historical data should be mapped on OpenHistoricalMap instead. Please folllow OSM's good practices: https://wiki.openstreetmap.org/wiki/Good_practice#Don't_map_historic_events_and_historic_features

On the matter of tagging, the seats=* tag is not for electoral seats, but for benches.

Best regards,

Casper