A passage in THE MAN FROM BARBAROSSA


#1

Could you, please, explain to me the meaning of a joke in TMFB. English is not my native language.
Chapter 7 Four Walls, p72 (Hodder&Stoughton hardback)

Give the Centre a bell, they usually have plenty of hard-weather gear to spare. Number’s 91, though nowadays you might even get a Porsche.

The question is: what is Number’s 91?


#2

I don’t remember this reference, but it sounds like he(?) is simply advising someone to make a telephone call to “Centre” and the number to dial is 91.