1980s children's book (possibly duology) about cloned boys

Question

What I remember:

• Published no later than 1990, probably more like 1985
• Near future setting, possibly featuring a vague Eastern/Western cold war scenario
• A boy of ~10 learns that he has a clone of the same age
• The clones secretly work together to ... do something that foils the plans of the adults who created them
• There may be a second book, where the boys learn there is a third clone
• The copy I read (US edition) was a slim hardcover of perhaps 150-200 pages
• Cover or dust jacket was primarily yellow
• Interior had some black-and-white illustrations, particularly on the end papers or near the title page

Any assistance locating this is appreciated!

Answer 1

Kept poking around library catalogs and doing keyword searches and I found them! And archive.org has copies for the curious — Solution: Escape and Code Name: Clone by Margaret C. Cooper.

In the 21st century, 13-year-old Stefan is sent to a scientific research station where his movements are closely monitored. He discovers he is a clone, destined to be part of a fanatical scheme to control the government

In the future, cloned brothers Evonn and Stefan escape from behind the Iron Curtain to search for their father in the United States