Meaning of "half-crown enclosure"

In the novel "Brighton Rock", Graham Greene refers to a "half-crown enclosure" in the context of horse racing.

My guess is that it may refer to a type of horse race where half-crown refers to a betting limit, or the size of the purse or payout.

Alternatively, the phrase may refer to a type of race track.

I tried searching the internet but found no explanation except for a few vintage postcards.

Any insights would be appreciated.

Solution 1:

A half-crown is an obsolete, pre-decimal British coin. A crown was worth 5 shillings old money (= 25p now) so a half-crown was worth 2s 6d or 12.5p decimal. There were 8 of them to the pound sterling.

A half-crown enclosure would have been a spectator area where the admission fee was a half-crown, probably with a better view of the track or finish line.

I can find 2 references to this phrase where the meaning can be inferred from the context
A report of the 1907 Brooklands 1st Race Meeting 7th paragraph
There is also a photograph of a spectator area entitled half-crown enclosure
and
an 1882 report of a horse race meeting in Australia

Solution 2:

Here is an example from the 1907 Brooklands 1st Race Meeting (an automobile race, in this case):