Welcome to the forum, and let me say some of us have big heads but it doesn't actually mean there are brains filling the space lol. I'll also say right off that I don't have any first hand experience with any C1AE blocks so I will just give you some general info, maybe someone else can fill in some details.
FE casting numbers are basically just a starting place for I.D.'ing a part, nothing is absolute and there is no complete definitive list anywhere. In many cases a single casting could be machined multiple ways. Casting numbers weren't always used and in some instances the same casting number was used on very different engines like the 390 & 427 and even totally different engine families. One other thing is you'll want to check if there is a complete casting number on the block. There should probably be a suffix letter after the C1AE-6015- "something". There were multiple C1AE blocks. Some examples are C1AE-6015-C, C1AE-6015-G, and C1AE-6015-V. But again, nothing is absolute, the suffix may have been left off when the block was cast. Unlike some brands, there are no "bad" FE blocks or heads ( in original form ), some just have features better suited to certain builds and some are of course more valuable.
You haven't said what you intend to do with this block, so again just some generalities here. the date code is December 12 1960, so it would most likely have been cast for a 1961 model year car. Ford was making both 352's & 390's in 1961. You'll have to check the bore and stroke to try and verify which. This is one example where the C1AE-6015-G casting block was used for both, so just the casting number isn't enough to go on. And to make things more muddy after 55 years even if it started as a 4.00" bore 352 someone may have rebuilt it and bored it to 4.05" 390 size already and it may not be suitable for a performance build without a sonic check. So one more thing is to try and look for clues if it has been rebuilt in the past.
Continuing with what you intend to use it for, early blocks like this one use the 2 bolt motor mount pattern so if you intend to use it in a '65 or later car or truck you may need to adapt the motor mounts. Also, most early cars used a generator ( alternators were a rare option ) and the early blocks often lack the later alternator mounting hole in the front of the block. Adapters can be made. There are other differences, none of which are insurmountable, just be aware.
One other thing of note, Ford had both Hydraulic and Solid lifter 390's in 1961 and many of the solid lifter blocks are not drilled in the lifter galley. The solid lifter blocks are a "score" but probably not a good choice if you intend to use a hydraulic lifter cam. If the price is right grab it and maybe trade it off for what you need.
Keep us posted with what you find and good luck.
