Oldies - 8 levels from "Sokoban" (1998) by William Fraser

"Sokoban" by William Fraser is an excellent online game in Java, active on the Internet since October 1998. It contains 190 levels. All the puzzles are made of known authors, except eight: the levels 51-58. The relationship of puzzles is the following:

Levels 1-50 are the "Original" collection.
Levels 51-58 are by author unknown.
Levels 59-98 come from XSokoban (levels 59 and 97 are easy versions of XSokoban levels 52 and 89, respectively).
Levels 99-190 are from Yoshio Murase, collections "handmade" and "autogenerated".

"Sokoban" (1998) by William Fraser, level 53

 
The eight levels "unknown" 51-58 are quite good, in old "Thinking Rabbit style". Especially interesting are the levels 53 (see image above) and 57.

Some time ago I wrote to William Fraser and I asked him if the puzzles 51-58 were his. This was his answer:

"I can't remember where levels 51 to 59 came from. The origional (first levels) cam from a spectrum program, and from 59 onwards came from a Japanese site (that I put a link to on the page). I think that up to level 59 came from the spectrum game (that would be about 20 years old by now), as I don't recall getting any levels elsewhere, but it's so long ago I could be wrong."

Therefore, levels 51-58 come from a Spectrum game. The ZX Spectrum is an 8-bit personal home computer released in the United Kingdom in 1982.

In addition, says William Fraser in the "Readme" (May 2000) in your Java game: "I copied most of the levels from a 8 year old spectrum game that was in turn based on an earlier game." Thus, the Spectrum game must be in by 1990.

I have searched in "ZX Spectrum Museum", but I have not found any Sokoban game... Then, I have searched in "World of Spectrum", and I have found up to 7 versions of Sokoban prior to 2005.

"Sokoban" by Hacker Chris, 1991, for ZX Spectrum

Finally, in one of the games, I have located three levels of Fraser. It's "Sokoban" by Hacker Chris (WE, Poland), 1991. The levels of Fraser 56-58 are the last three of the game of Hacker Chris, levels 53-55. The last level of Chris (#55) is unsolvable, but in the version of Fraser appears arranged, perhaps by the own Fraser (?).

The other puzzles by Chris 1-50 are the "Original" collection (taken from the IBM version of Spectrum HoloByte). Levels 51 and 52 is the level 18 of the "Original", repeated (#51 is an easy version).

I have not found who are the other five levels of Fraser 51-55.

To play online "Sokoban" by Hacker Chris, click here. 

"Sokoban" by Hacker Chris, level 54

  
A curiosity. The puzzle of Evgeny Grigoriev, Grigr2001 #1 Bardak, first in the collection, seems to be a remodel of Fraser #57 (= Chris #54, see image above).

You can download the 8 levels from William Fraser here:

• from Sokoban by William Fraser

The question is: Who are the others 5 puzzles of Fraser 51-55? Can anybody provide more information?