I just had a really odd idea for an SCP/Tale/Anomalous item. Here goes:
The Foundation finds a large metal box buried somewhere deep underground in a conspicuously odd place. Upon recovery, the box is found to be hundreds of years old, but appears to be made of modern materials. Inside the box is another box with a timed lock mechanism set to unlock on a date coinciding with the [REDACTED]-year anniversary of the operation of Site 19, as well as some carefully preserved Foundation documents detailing some kind of potentially Keter SCP, how to contain it, where to find it, …and when to start looking. Documents are found to be genuine and by following procedures therein the SCP detailed within is located and contained, and analysis of the SCP reveals that it was actually recovered in an incomplete state, and analysis of the documents and the object reveal would be capable of causing an XK-end of the world scenario with the addition of several key components, which it currently lacks, so the object is sabotaged to be unable to accept these items as a precaution.
Disaster averted, all that's left is that other box with the timer. Date comes, box opens, inside are several bottles of wine, aged to perfection courtesy of the box's apparent nature as an out-of-place artifact, as well as a handwritten note by a known Foundation staff member revealing the box to be from an alternate future Foundation, sent to the past in a last-ditch attempt to avert a global disaster brought on by the SCP, with the wine added as congratulations in the successful containment of the SCP as well as for Site 19 reaching its hefty [REDACTED]th year of operation.
…a year the "other" Site 19 did not survive to experience.