Excellent! Did you ever open it to check inside? If you're afraid to do so (understand) would you mind:
1- Check if a advertisement screen appears after stage 2 or 3 which displays release date, price or other promotional things?
2- Or check the weight of the cartridge (in grams) so we can compare with others
Thanks to you we may confirm a theory...exciting!
I dumped my copy and it's 100% identical to the final retail title. Mine doesn't have mask ROMs, but it's not EPROMs either, instead being a third category of "OTP" EPROMs that only allow for single time programming (not that this matters). Again, no Gradius sample cartridge is known to have a promotional segment because as previously stated the known copies out there that are legitimate are literally the retail game.
Well some have differences even though meant to be store samples...and large amount of samples were using EPROM especially Konami. That's how most of collectionners are used to check authenticity by the way (when it's known). Here an exemple with the FC Goonies sample in my collection (that I used for comparison). If you have a copy with mask roms, then it's a fake...like many on YA sold by a famous Osaka con man.
Personally I don't think this is a good frame of reference in this particular case. Too many official Famicom games use standard EPROMs, or have OTP EPROMs (which look
exactly like Mask ROMs to those unaware), and in the case of Gradius it's clear the sample cartridges were produced so late in development as a promotional item that they host the retail title regardless of what ROM chip type they're using. On top of this, Gradius (FC) is already a port of an existing game, so it's not surprising to me that there wouldn't much for differences anyways.
By the way, I know exactly what seller you're referring to, he's made a name for himself.
To be honest I don't know what you're talking about here? The video links to the Salamander prototype he owns, which I'm already aware is a unique version of the game with a promotional screen. But I was specifically referring to that thread with the multiple links where I inquired
specifically about the Gradius Sample cartridge and he replied saying that
Gradius specifically had no differences from the final game that he could tell of, which perfectly aligns with my Sample cartridge exhibiting the
same exact lack of differences.
Well that's - slightly - more...Mine has #374. So far I sourced in recent years 008/126/159/332/374/522/549 which includes yours and the JP collectionner you mentioned. The number is also hand written on the white box of the cartridge - I have the same with Rampart (for which there is another ongoing story but let's solve this one first

)
That's interesting. I guess it's not surprising these Sample cartridges had their own unique boxes but I'm still somewhat surprised to hear about that. Is there a photo of this? I guess it's nice to know my estimate wasn't far off either. But it's just another example of your cartridge being more legitimate.
Well I would have thought so too...but I got same number on Goonies sample and that's obviously not from a retail batch as per photo above. So I figure there is maybe something about it but can't tell what.
I think you do have a point, but the main reason that I'm still skeptical is because I've just seen random batch codes like this appear in a few random Konami titles. Retail Lagrange Point in my case has something like this. Although that game is much later than Gradius (and by quite a while too).
I'm curious what that "extra info" you have is, though.
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All of that out of the way, I'm confident in saying that your cartridge is legitimate, as far as Gradius and its samples are concerned, but again I don't think much of what's mentioned here matters too much (aside from I guess the hidden cartridge batch code?) since the cartridge itself already is overwhelmingly showcasing it's a legitimate Sample cartridge.