A determined IC attacker could try an easy way to check whether this chip was actually an ASIC. The easy way is to note which pins are connected to power supply, ground, clock, reset, serial, and other interfaces, and to compare all this information with the database of suspect microcontrollers or other mcus. This works very reliably, as each microcontroller family has its own characteristic pinout. Once similarities are found the suspected microcontroller could be verified by placing it into a programming device or universal programmer and trying to read it.