l_inc wrote: 
Quote: 
Why, for the frak's sake, 50?!


Probably the least number of seconds ever elapsed between two successive versions of fasm.


This is actually a good point.
But in truth, I just experimented with a few values and selected the first one that looked OK to me. I wanted no more than five characters, but with still enough precision to increase when fixes are applied just a couple of minutes later.
Now that I think about it more, I find that I could invent some "reasons" why 50 is a good choice (or at least an "OK" one). The range of the last two digits is 36*36*50 seconds, which is a rough approximation of 2^16 (but it is also just an exact 18 hours). Therefore the first three digits/characters represent more or less the high word of timestamp, and the other two  the low one. Only the first three digits are usually going to matter, but the additional two may make any particular number more recognizable.