as used until then


The formation of the Haudenosaune Confederacy called for a more complex method of communication than wampum as used until then had provided.
This sentence is an answer choice from one question of the LSAT Preptest.
How to understand "as" in this sentence? I think it's a conjunction used to introduce a clause. It is actually "wampum as (it had been) used until then had provided" with the subject and be verb omitted?
Thank you in advance for your attention to this post.
  • Charles12

    There are two meanings if as is used as a preposition:
    1. used to refer to the function or character that someone or something has.
    2. during the time of being (the thing specified).
    I don't think "as" in the sentence is used in either of the two ways.