When you loved dolls and studied them, you started to love all kinds of people too, because you saw the virtue in their expressions, how carefully they had been sculpted, the parts contrived to create the triumph of this or that remarkable face.
The subordinate clause in this sentence, headed by because is the finite clause:
- you saw the virtue in their expressions, how carefully they had been sculpted, the parts contrived to create the triumph of this or that remarkable face.
This clause has a Subject you and a Predicate, a verb phrase, headed by the verb saw. The Direct Object of the verb saw is a co-ordination of three phrases:
- the virtue in their expressions
- how carefully they had been sculpted
- the parts contrived to create the triumph of this or that remarkable face.
In other words, this clause means:
- You saw [the virtue in their expressions], you saw [how carefully they had been sculpted], and you saw [the parts contrived to create the triumph of this or that remarkable face].
We are interested in that last phrase, so we can look at this clause without the first two phrases:
- you saw the parts contrived to create the triumph of this or that remarkable face.
This clause contains a noun phrase headed by the word parts. This noun phrase is being modified by a past participle which has a passive meaning. This is the word contrived. Participle clause like this can be analysed as "reduced relative clauses". A relative clause can be reduced in this way by dropping the relative word (either which or who) and some form of the verb BE:
- The man who was standing in the corner ... ---> The man standing in the corner ...
- Any staff who are required to attend can ... ---> Any staff required to attend can ...
In our example we can understand the noun phrase like this:
- the parts which had been contrived to create the triumph of this or that remarkable face.
The verb contrive means to deliberately use your skill to create a special effect. We could substitute in the verb design, which would give us a similar meaning. This gives us the following kind of meaning:
- You saw the parts which had been designed to create the triumph of this or that particular face.
The Original Poster's questions
The word how has not been omitted from the beginning of this clause. However, the writer could have used a structure like that instead:
- You saw how the parts contrived to create the triumph of this or that face.
In this sentence the writer would be poetically giving the parts of the face a kind of will of their own. The meaning would be that the parts were trying to create an effect. However, this isn't what the writer chose to do. The order of the words would be very similar, but the actual grammatical structure would be very different.
We don't ever really know why a writer wrote things in this particular way and not a different way. But we can guess. I believe the writer chose to say this or that remarkable face and not their remarkable faces for a couple of reasons. The first is that the writer does not want to say that all the faces were remarkable. The second is that they want to say that you could see this in any particular remarkable face that you found - for instance maybe this one, or maybe that one.