Complex sentence: According to a copy of the document on a new engine research, labeled "Gessellschaft", a test piece was developed, however, it was revocated along with the plan itself before the full-scale production could take place.
Split into simpler sentences: According to a copy of the document on new engine research labeled "Gessellschaft", a test piece was developed. However, it was revoked along with the plan itself before the full-scale production could take place.