A present participle is called “present” only because of its form; it does not express tense like the finite verb in a sentence, but only establishes time relative to the action/state of the main clause. In your example, it’s helped along by a time expression.
With a present participle, the action/state described takes place concurrently with the main action/state, whether in the past, present, or future.
From very small beginnings in the Greek coastal trades, the Chandris family company developed into a renowned concern, at one time operating some of the most famous liners in the world. — Amazon
Since developed is in the past, so is the operating.
If one wishes to express an action/state prior to the main one, you can use a perfect participle:
In addition to his racing activities, Mr. Shaw is widely known in the aeronautical field, at one time having operated a training school and passenger service line in Los Angeles. — The Rubber Age 46–47 (1940), 401.
This is analogous to using the past perfect: it’s only necessary when the time difference between two past events is topical. In this case, it’s because Mr. Shaw is now primarly engaged in racing, but is still known in aeronautics because he had at one time operated a flight school and run a passenger service.
Whether you use a participial phrase or express the same thought with an independent clause is a matter of style, but the construction can improve the flow of a paragraph and by subordinating one bit of information to another more transparently express their relationship.