Note: This is another in my sequence of post-Mystery-Hunt cryptics, which started with "Still There," "Post-Game Predictions," "The Sequel," "Power Lines," "A Lesson in Cryptography," "Yet More Villainy," and "Further Escapades"; this one was written before the 2011 hunt and refers to the 2010 hunt.

After all that work repairing the fabric of time, you deserve a break: To find the coin, just look at the top of the page.

What's that? It's not there? Oh no! The coin has come unstuck in time again! This time, though, it has only traveled back 100 years, to 1910. To find it, you must solve this puzzle from 1910's "Puzzles of the Future" Hunt (Round 3: Word Squares Go Wild). Unfortunately, each of its Across answers, when entered in the grid, will be affected by one of the chronological anomalies between then and now; specifically, each of the following changes applies to four Across answers:

1. (2010) One letter turns the clock back 3 hours.
2. (2009) A Core Reaction occurs.
3. (2000) The answer transforms into numerous appropriate items from the movie The Wizard of Oz.
4. (1983) A certain movie character goes home.
5. (1952) One letter ceases to be under "their" insidious influence.
6. (1926) Like Metropolis, the answer is cut to half its original length.

In addition, all of these changes will affect another important group. Each Down clue contains one incorrect letter that must be corrected before solving; the incorrect letters will tell you what group to change, and the correct letters will tell you what changes to apply in what order. (Apply the first two changes in that ordering to the first word, the next two to the second, and the last two to the first word again.) Doing this will lead you to an entity that can set everything right; however, in this case you don't need any of this entity's special abilities — all you have to do is "re-solve" by looking again at the TOP (but not the top of the page, this time) to find the start of the path to the (entity-appropriate) coin.

ACROSS

1. Toss around stuff next to bachelor making eggs
5. Leaflet mischaracterized rifle
10. Actress Greta discarding ring and dress
11. Every other item from (say) Amy's discount clothing chain
13. Sailor claims that hurts, in German and without proper decorum
15. Flying mammals try turning
16. Said "hi" to mostly-inexperienced time traveler played by Keanu
17. Early musical pieces from revues rot badly
18. Hole that supplies water in a proper manner
20. Something thrown by Dotty, Joel, Rip, etc.
23. Discussed what you might hear from reporters and antelopes
25. Clears fish-catching devices
27. Leave someone who gives tips about an appliance company? (2 wds.)
28. Fellow from the Emerald Isle is hot at first, mostly in Persia
29. What Gene Kelly was doin' in the rain with evil spirit (var.)
30. Signs of assent and denial disheartened debs
31. One in a state about one zit I cured partially
35. After a cold, that guy had exhibited a flu symptom
36. Delighted expressions go away after reflection
37. Old friend's iridescent gem
38. Surprisingly, there's more than one compound containing C-O-C
39. Left state with . . . um, fish
40. GI is convinced that is real
41. Cleaners of Spanish shelters getting a bit of work

DOWN

2. Would very gladly rant at fora, ultimately interrupting CO (5 2)
3. Later dropping with ridiculous speed (4)
4. Those that begin staring, at length, into a merely 80-proof drink from Sweden (7)
6. Biblical unit used to measure Grampa Simpson's eon with no horse (4)
7. Antelope, rearing up, start to diss the country the corn is from (4)
8. Am the first among five forest-dwelling couples to produce dishes (7)
9. Help muse accept quiet bribes (4)
12. Enzyme that breaks down (NH₂)₂CO in tusk from upriver with ease (6)
14. Character with two corneas confused son a lot (4)
15. Countenance six initially stealing silver and piece of plectrum (6)
19. Number will be in alto nincompoop's fach soon (4)
21. Retry snare section (4)
22. Frost is removed from spring celebration's flowers (6)
23. Couple of guys barely sing each note from an African aria (7)
24. Culler of evergreens and dock around Indiana (6)
25. The author and salver claiming trendy Missouri's upsettingly attractive (7)
26. Gall's your topic, essentially, when filling in Dole and young Newt, say (7)
29. Foursome held back by cape-using plaintiff (4)
31. Catty remark about trouble and the filth of November (4)
32. Fall in the crevices Calvin Klein's opening (4, var. spelling)
33. Finally stick needle that's been cleaned in the middle part of the leg (4)
34. Lock up venter from south Utah (4)