This looks like a possible marriage for Isaiah and Maria:

Marriages Dec 1933

Smith Isaiah Smith Leeds South 9b 1038
Smith Isaiah Booth Leeds South 9b 1038

The double entry is because Maria's name is given as "Smith or Booth", suggesting that she was already using the name of Smith prior to the marriage.

Getting this marriage certificate should not be your first priority, though, as there will be nothing on it to prove that it is the right one. What you need is Arthur's birth certificate, which will show both parents' names and the father's occupation.

There are a number of possibles, especially as Maria(h) may have given her maiden name as either Smith or Booth. But the father's forename is nice and distinctive, so your best bet is to apply to the GRO (via www.gro.gov.uk) for the birth certificate of an Arthur Smith, born in 1928 or one year either side with father's name Isaiah. If no match is found, your £9.25 fee will be refunded. I would very much advise against giving any more detail on the online form. Hoping that the father's forename is right (presumably from Arthur's marriage certificate?) is one thing, guessing anything else might result in the GRO failing to issue the certificate you are seeking.

Hope this helps

Caroline