It looks as if (maybe) the internal bayonet part might have been chipped, which is rather unusual, but it might still safely hold a lamp despite the slight damage.
OP - the lamp is a BC (Bayonet Cap) lamp which is the most common type in the UK. Best to use an old fashioned filament type lamp rather than an LED type. LED ones like to run with plenty of cooling ventilation, which it would not get in that fitting, once the lens is fitted.
40 or maybe 60w - but it looks as if a Max size might be stamped inside the fitting.
One concern is that it will get quite hot in the fitting and that grey PVC cable is not suited to a lot of heat. Usually a new fitting will be supplied with heat resistant sleeving to slip over the PVC wires.
If you need to find a tradesperson to get your job done, please try our local search below,
or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Please select a service and enter a location to continue...
Are you a trade or supplier? You can create your listing free at DIYnot Local