Complex sentence: Mr. Adams was a partner in the firm of Adams & Rigg for much of that time, though the arrangement may have only been formalized later, as late as 1946, he is given recognition as a sole-proprietor.
Split into simpler sentences: Mr. Adams was a partner in the firm of Adams & Rigg for much of that time. Though the arrangement may have only been formalized later, since as late as 1946, he is given recognition as a sole-proprietor.