I think the issue is how the tickets are printed. With most packs having nothing but the minimum guaranteed amount of prizes, those are printed in bulk with a select few being diverted for additional wins to be added. For economy sake, the fewer packs you divert for additional prizes, the lower your costs so the printing company is going to try and put as many winning tickets onto the same pack as the contract will allow. This results in hot packs and cold packs which are shuffled before distribution so the only way to identify a hot pack is by observing actual wins. Chances are the contract will divide the prizes into tiers with different requirements to the printer for the respective tiers, the low tiered prizes are probably expected to be as evenly distributed as possible and are probably what guarantees the minimum prize amount per pack hence allowed to be reallocated as needed to meet the contract, the mid tiered prizes are probably the ones that the printer has the most leeway in combining to save on costs while I suspect that top tier prize distribution clauses are probably very specific.
This is probably what's behind the myth of the black L mark. Those are alignment marks for the printing presses and a L in a corner would indicate that it was in the corner, hence edge of a sheet or at least edge of an alignment grid. The print dies at the edge of a sheet are the easiest to access for modification and as each sheet are folded and cut into several packs, the assumption is that once the packs are separated from each other, they can be randomly shuffled before shipment, the pack numbers having been algorithmically assigned prior to the assignment to the printing die so as to avoid identification of the higher paying packs by pack number.
I suppose that if the ticket has or is from the same pack as one that has a "L" or "|" mark then it is on the edge of a sheet. If it has or is from the same pack as a ticket that only has the "-" mark then it's definitely not from the edge of a sheet. If it has no mark and is not from a pack with marked tickets then it's origin is unknown unless you bought the entire pack in which case there should be some tickets with horizontal marks.
However I suspect that diverting packs cut from the edge to be unlikely, it would be easier to simply print entire sheets of the hot packs and then shuffle them with the rest of the packs. But it is conceivable that the sheet stamps for the hot packs are smaller or require more careful alignment hence tend to have more alignment marks.
Of course, with concepts such as inkjet printers, these idiosyncracies of the printing process are probably going to go away in time. However, the printing presses are very expensive and the qualification and acceptance of new equipment is very slow so we may still be able to take advantage of how they print the tickets if only we knew how they did it.
Maybe someone here might have some inside knowledge of how the tickets are printed and can comment.
Maybe people can post about whether or not their tickets were on the edge or not and their respective prize amounts if any so that we can benefit from a greater pool of observations. I have scans of all my tickets so my data for the Texas Lottery is as follows (note, I really didn't start playing till I got the $1,000 hit):
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$500,000,000 BlockBuster 1114
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Non-Edge
5x losing tickets
2x $20
1x $25
1x $30
Edge
16x losing tickets
4x $20
1x $25
1x $50
1x $100
1x $200
1x $1,000
Unknown
15x losing tickets
4x $20
1x $25
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Super Set For Life 1024
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Non-Edge
Edge
1x losing ticket
Unknown
18x losing ticket
1x $20
2x $25
1x $30
1x $25
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Set For Life 1057
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Non-Edge
Edge
Unknown
6x losing tickets
1x $20
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Big Money Bingo 1069
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Non-Edge
Edge
Unknown
10x losing tickets
2x $5
2x $10
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Double Doubler 1206
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Non-Edge
Edge
Unknown
1x losing tickets
1x $1
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Weekly Grand 1153
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Non-Edge
Edge
Unknown
5x losing tickets
1x $2
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Break The Bank 1047
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Non-Edge
Edge
1x losing ticket
Unknown
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Stocking Stuffer 1188
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Background is black
Unknown
3x losing ticket
1x $5
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Jingle Jumbo Bucks 1192
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Non-Edge
Edge
Unknown
1x losing tickets
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$50,000 Cash Winfall 1184
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Non-Edge
Edge
Unknown
1x losing ticket
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Monthly Bonus 1062
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Non-Edge
Edge
2x losing tickets
Unknown