10.3 Was für eins möchten Sie denn?

10.3 What is the function of eins in this sentence? I am familiar with the expression was für ein... but this seems different. Is it just the numeral "one" or something else.

I have found some other examples:
Trinken wir noch eins.
Eins wollte ich noch sagen.
Es ist mir alles eins.

Is it a form of the indefinite pronoun einer if so why not eines?

Don't worry, I found the answer it's the neuter indefinite pronoun eines with the "e" omitted. 

Hallo sfpugh,

The expression “was für ein“ is used as an interrogative pronoun (question word). It can replace or accompany a noun or pronoun which is asked for in the question and has to be declined to match its case, gender and number.

Another way of saying

“Was für eins möchten Sie denn?“ - “What type would you like?“

would be

“Was für ein (Auto) möchten Sie denn?“ - “What type (of car) would you like?“

or

“Welches (Auto) möchten Sie denn?“ - “Which (one/car) would you like?“

You see, the noun Auto is actually not needed in this question, hence it is replaced by eins.

Let me give you some more examples:

“Sie hat einen Hund [masculine].“ - “She has a dog.“
“Was für einen (Hund) hat sie?“ - “What type (of dog) does she have?“
“Einen deutschen Schäferhund.“ - “A German Shepherd.“

“Sie hat eine Katze [feminine].“ - “She has a cat.“
“Was für eine (Katze) hat sie?“ - “What type (of cat) does she have?“
“Eine Maine Coon.“ - “A Maine Coon.“

“Sie hat ein Auto [neuter].“ - “She has a car.“
“Was für ein Auto hat sie?“ - “What type of car does she have?“
“Einen BMW.“ - “A BMW.“

“Sie hat ein Auto [neuter].“ - “She has a car.“
“Was für eins hat sie?“ - “What type does she have?“
“Einen BMW.“ - “A BMW.“

The “s“ in “Was für eins“ is needed when replacing a noun which is neuter.

Hope this helps.

Grüße
Julia
 

Thank you for the explanation