The great majority of Simplified Chinese characters* were created during the simplification process in the 20th century in the PRC. What is however probably not very well known is that a lot of what we call Simplified Chinese Characters today are characters that are very old themselves.
These characters may have originally had meanings that were not the same as the characters they replaced in the simplification process, or they sometimes were alternative modern or older versions of the same character but in either case, these Simplified Characters existed for a very long time in history as well (as will be shown, often for more than 2500 years).
The point of this post is not to argue that all Simplified Chinese characters are old, or praise their age and neglect the fact that they don't corrupt the phonetic and semantic elements of Traditional characters they replaced. I'm simply stating an interesting fact and addressing the common misconception that all Simplified Chinese characters were created ad hoc in the in the simplification process in the 20th century.
Furthermore, the simplification in the 20th century by the PRC government wasn't the first one in Chinese character history. There were several ones, some large-scale and systematic, others having the nature of random improvements, with the 20th century one being the most recent one. These previous simplifications also often corrupted individual character elements rendering them irrecognizable as will be shown below.
To name just a few all following Traditional characters had previously been simplified with their originals clearly containing recognizable phonetic and/or semantic elements:
年
Original meaning "to harvest grain" formed by 禾 (meaning grain) and 千 phonetic (pronounced qian1) originally written as 秊
https://ctext.org/dictionary.pl?if=en&char=%E5%B9%B4
表
Original meaning "outer side of garment" formed by 衣 semantic (meaning "clothes") and 毛 phonetic (pronounced mao2) originally written as 𧘝
https://ctext.org/dictionary.pl?if=en&char=%E8%A1%A8



