The chokes you will have to get measured, there is no 'standard' choke nor do the proof marks tell you anything about choke.
Could be anything from F/F to Cyl/Cyl.
If you haven't had the chokes measured, I doubt you have had the wall thicknesses measured which is a safety issue rather than a use-ability issue. I suggest that you find a friendly gunsmith with the necessary gauges and get him to do a full report on the state of the barrels.
As to 'base model', I don't know enough about Coggy's but the engraving looks about standard, only the missing side plates point to a lower model.
Note that it is chambered for 2 1/2" cartridges so you should not put any 2 3/4" cartridges anywhere near it.
You might be able to review the above once you know the state of the barrels but certainly not until.
