while not Enigma related, Marian Rejewski and his colleagues, if I remember right, reconstructed physical Enigma (pre-war, 3 wheel) machines only from analysis of encrypted traffic, beating the French and English mathematicians working on the "enigma problem". it was pretty big and IMO comparable to Tuttes successes with Lorenz, it's annoying that history forgets Rejewski and his contributions so quickly.
More accurately, the British and French had not managed to make any progress decrypting the Enigma until the work of Rajewski and the Biuro Szyfrów was handed over to them due to the shifting political situation.