The Air Challenger EG804 (also sold in the USA by WGP as the MG7) was released in around 2008 and sold for around $80 US.
Made in Taiwan, this is an electronic spool valve marker that consists of a die cast frame wrapped in two plastic shells. It’s quite an interesting design and features a very short action. The battery actually sits in a cavity behind the bolt. It would be difficult to clean though because the whole marker needs to be disassembled to access the bolt. The maker’s specs include 15 BPS, dual beam eyes, dual detents, adjustable trigger and cocker threads.
This marker has a very cheap feel about it and wasn’t a big seller but it was well liked by some buyers. Surprisingly, Air Challenger are still around and this marker is still listed on their web site along with a bunch of others.