Before the stat nerfs, there were 3 tiers of gold stats. I'll just use attack as the example.

Highest tier rolls up to 80, available only on red gourds.

Middle tier rolls up to 70, available on any tool found in BF TI. Medium and hard BF has a much higher chance to roll stats from this tier.

Low tier rolls up to 50, available on any gold tool. All gold tools obtained from any TI must roll stats from at least this tier.

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After the nerf, only the lowest tier of gold stats has a CHANCE to show up on red gourds. (with the +4 res ones being missing altogether). All other gold tools can no longer roll gold stats.