BSA L prefix were made between 1919 and 1936
Yours has the later style of stock and semi high serial number, so I would say 1930 onwards as for age (could be wrong, might have just had a stock change).
No Idea what the mark on the wood is, could just be from the retailer.
Some rear sights had the patent number on.
The number 1 above the pellet hole just signify's its a "number 1 bore". Meaning its .177.
Condition wise it is pretty standard, neither good nor bad. One thing though, does it have any etching left on top of the cylinder? If it does the value will be a bit higher.
Stock marking 14 1/4 means its a 14 1/4 inch stock which is what most had so again, pretty standard.
So looks like a pretty standard L pattern BSA. Quite popular with bell target shooters since they are deadly accurate and not too unwieldy to handle.
Price wise I would say between £140 and £170 (my opinion based on what I can see in photos) Add a bit more if etching is still visible.
Someone on here tried to sell a similar L pattern for £200 I think. Ended up breaking it for spares since no one showed much interest at that price.
So somewhere betweeen £140 and £170 seems good and at that price I dont think you will have it for much longer. Very popular air rifles due to their quality.
Again all my own opinion based on the pictures and what I have seen them go for.