CBeing new to 99's all the letter designations can be confusing.
Biggest differences between 99's are usually:
1) the stock configuration
2) the barrel length and profile
Then add in the serial number range can make a difference. Only once in a while is the receiver itself is different.. the saddle ring carbine has holes for the staple, the 284 rotary models have different internals, the post-1960 99E is different than the others with a lever safety, etc.
