When not being studied, SCP-XXXX should be placed in refrigeration at all times. Refrigeration must be done via means of a standard cooler, or ice-box that should be filled with ice until half of the maximum volume of the box is used up.
I doubt the need to go into specifics like this. It's probably better to just state the maximum temperature and move on; it reads easier with less unnecessary detail. Think about it: The brightest minds the world has to offer probably doesn't need instructions on how far to fill a cool-box. Say something like ''Below 7 degrees Celsius'', they'll figure it out.
Any researchers wishing to study SCP-XXXX are to observe the object no longer than an hour to prevent a complete shutdown and failure of SCP-XXXX.
Same here, a sentence like:
''When testing, observing the object longer than 60 minutes is prohibited.''
Is enough.
Contrary to all observed properties, SCP-XXXX must be treated as living at all times.
What does that mean? Treated as living in what way? This is too vague.
SCP-XXXX appears completely anatomically correct when compared to a living heart, matching in both size and height.
Two things: Firstly, 'appears to be' indicates that something isn't actually that what you reference. If something is anatomically correct, call it anatomically correct. Secondly, size and height are part of the same measurement. If it were me, I'd take the size and height bit out entirely.
or beat at a pace consistent with the human heart's known properties.
You might want to change this to something like:
''or beat at a pace consistent with the average heartbeat of a healthy human of [AGE HERE].''
OR
Give it a BPM (beats per minute) instead.
No source has been found for this beating through means of direct observation or X-Ray scans of SCP-XXXX.
What do you mean 'source'? Hearts outside of a body can beat with the right electrical impulses; tricking the heart into thinking it's still attached to a brain can make it beat on its own. Instead of X-rays, you should be looking at electromagnetic fluctuations.
SCP-XXXX is currently theorized to be a part of two or more separate objects, however, no matches have been located to SCP-XXXX at current time, and no origin or creator has yet been discovered behind SCP-XXXX.
Okay, so if we have no leads on it, why do we think they're part of a set? Keep in mind that as the author, you know the entire story, but the Foundation needs to have discovered what it knows about the SCP object through observation and experimentation. You'll need to convince your reader that someone with no prior knowledge whatsoever of the anomaly managed to somehow figure out (not magically know!) all the information you've got in the article.
SCP-XXXX has been observed to never output the same deity more than once, nor will it output more than one card for one individual.
You're going to run out of deities eventually though, unless you count the countless pagan and pre-classical history ones.
In this state, subjects have been reported as undergoing a substantial change in mood and identity.
Both of these are vague at best and non-clinical at worst. 'Mood' could be changed to something like 'psychological state' and 'identity' to something like 'sense of identity'.
Subjects have shown to either turn violent or benevolent in regards to their new identity.
Perceived identity?
While undergoing this new identity, subjects appear unaware of current surroundings or people, and perception of reality becomes distorted.
You said the same thing twice here. I'd keep the first part.