JMHO, £80 or so, there's lots of them out there and boxed/complete one's always turn up sooner or later at a reasonable price.

Dating wise, the barrel extension and fore-end script can help in this respect, but I'm not aware of serial numbers being used on these items over the production period.

Regarding pricing advice for selling, listen to "definite offers", anything else might be offered as a means to "boosting the market" for others wanting to sell similar in the near future.

HTH, Vic T