GrahamClayton: Here are contemporary annotations from the "Field", reproduced in the "Illustrated Sydney News", dated 28 February 1891:
4. c3 - 4. d4 is justly considered preferable
4...d7 - 3...d6 is one of the oldest defences to the Ruy Lopez. Mr Steinitz brought it into prominence within the last few years; but on this occasion he deviated from the more usual move 4...f5, in favour of the text move, which is less enterprising.
5...ge7 - anticipating 6. d4, when 6...g6 would defend the king pawn.
7. d5 - This advance is only in Black's favour; especially as White follows it up by exchanging his Knight's Bishop, when clearly Black's game is far better developed. 7. e3 and bd2 would seem better.
9. a3 - Bringing the Knights out on the wrong squares seems contagious.
10...c5 - Commencing already an aggressive movement with this well-posted Knight.
12. b4 - This move still more compromises White's Queen side, without even getting rid of the troublesome Knight. He might have guarded first against the entry of Black's Queen to g4 by advancing 10. h3, leaving the Knight temporarily undisturbed.
14. c4 - Still more weakening. The alternative move 14. g3, however, is after all only a choice of evils.
16...ae8 - Mr Steinitz, having the game in hand now, makes a useful developing movebefore proceeding with the final attack. It is perhaps over cautious in this instance.
17. fe1 - From bad to worse, nut it is a natural consequence of his faulty development.
17...g5 - The decisive move.
18. g3 - If 18. xg5 xg5 19. e3 seems to be forced.
18...c3 - Winning the exchange and the game. The rest is uninteresting, and only a matter of time. Mt Steinitz played the game with irreproachable correctness; but even a second-rate player would have won the game as played by Mr Gunsberg.