Diamond Credit Union. 1600 Medical Drive Pottstown,Pa 19464.All Products. All Services. For All People. The largest full service credit union serving Berks County and the tri-county Region. 610-326-5490 Pottstown member service center.610-396-9980 Reading member service center 1500 Ethan Drive, Wyommissing,Pa 19610. 1-800-593-1000.www.diamondcredcu.org . Your savings are federally insured to at least $100,000 and backed by the full faith and credit of the United States Government by the National Credit Union Association, a US Government Agency.