Trying to buy interior doors

[WelshSkippy]

Hello!
I am looking online for oak 1930s style doors. A lot of doors I am finding say DX doors PP style. I have no idea what DX or PP mean.
I have tried googling this but found nothing.
Any ideas?
Many thanks.

 

[Harbourwoodwork]

Have you tried reclimation yards,You may have to haggle the price down ,they not selling an old door but trying to sell you a piece of history,well in their eye's , most of the off the peg door's may not have the style or quality easpecially from the shed's,Another option is have a door made at a joiner's shop,Do you have a style in mind?