最近看一本高频交易的书，其中两页接连出现"prime services"这个词组，不知道是什么意思。
第一句是：“Most investment bank offer leverage through their 'prime services'“。
下一页又有一句：“In addition to providing connectivity to exchanges, borker-dealers typically offer special 'prime' services that include safekeeing of trading capital and trade reconciliation.”
请问高手，这里的prime services到底如何用中文表达？