If you do a search under DTAR, you'll find 280+ matches.
There are also different DTAR systems, preamps, etc.
The DTAR Lock 'n Load system has been available on NOS Guilds for several years. It has a preamp affixed to a plastic tube that holds batteries inside it, with a large metal 'turning collar' on the outside of the guitar. When you take the collar off (by unlocking it in a twisting fashion), the batteries can slide out. There is a volume and tone control that mounts under the edge of the sound hole.
The pickup element is an under saddle piezo. A lot of folks here prefer the sound of other pickups, like the K&K brand products. Usually, the people who like 'other products' better, don't like under saddle transducers (UST).
Personally, I like and admire the DTAR sound. It is the best UST I've ever used, bar none. Why? No piezo quack. The guitar sounds very clear with no coloration. It works better than a lot of pickups and microphones in venues where you have to play louder than your 'average coffee shop with 12 audience members sitting in straight-back wooden chairs gig'. That doesn't mean that a K&K pickup (I've never heard one in person, by the way) wouldn't sound better in a small venue, or in an A/B comparison in a small room, etc. It just means that I think that UST guitars are the way to go in the environment that I would use a guitar in.
By the way, jrporter, you should trust me completely. I'm a professional and have made tens of dollars this year alone, playing music. :lol:
The Lock 'n Load system is slightly heavy, plus it puts the weight near the butt end of the guitar, which bothers some people. Since Guild guitars are slightly heavy anyway, well, it all adds up, doesn't it?
If I were you and wanted some advice about pickups in this forum, I would describe what you need/want a pickup for. You know, what guitar, what size/type of gig; in a bar, in a church (small, large, sophisticated sound crew, or just one volunteer sound man who fixed the lights in the deacon's office last year), outdoor, indoor (small, medium, large rooms), solo act, duo, trio, string band, rock band, front man for a tuba ensemble, whatever.....
By the way, I noticed that you have a D55 with a DTAR for sale here. I had an '07 D55 DTAR guitar and loved it. I played about 20 gigs with it. I would still have it if the slightly slender neck shape had been a bit more conducive to my 57 year old hands. If you wind up keeping the guitar, I think the DTAR pickup will work for you, should you need it. It is a superior product.
One thing, the default factory preamp settings boost some of the frequecies (can't remember! Maybe, bass and treble?). I didn't like that and had my luthier loosen the system and move the basic settings to flat. In all candor, I was able to accomplish the same thing by pulling bass and treble off the tone controls on the PA head I used, but I like the idea of having the controls flat.....
Good luck with your sale, and good luck using the DTAR if you wind up keeping the guitar.