TNG Combadge

The TNG Combadge is a piece of equipment worn by all Starfleet officers, starting from Star Trek: The Next Generation onward. This combadge was worn in TNG, as well as Seasons 1-2 of Star Trek: Deep Space 9, up until the release of Star Trek: Generations, where it was replaced with a new design.

History and Design
In series such as Star Trek: The Original Series and Star Trek: Discovery, Starfleet officers generally wore pins or patches designating them as Starfleet, or to a particular ship. The TNG Combadge was created to combine the function of identification with the utility of the communicator, another device from TOS. In universe, they are utilized as a way of communicating with other Starfleet officers serving on board the ship/within range, and also with the ships computer. The latter effect is most commonly used when trying to maneuver a runabout or activate an emergency function. The Combadges function by either tapping on the delta, which generates a "chirp" sound, or by just speaking out loud in some cases, depending on circumstances.

The TNG Combadge was designed by Rick Sternbach in 1987, during pre-production of TNG. Many designs were considered, but ultimately, the production settled on the final design: a metallic bronze-gold oval with a matte light-silver Starfleet delta on top. The silver delta has a black outline that runs the depth of the delta down to the oval.

Variations
The TNG Combadge saw many one-offs and variations, as well as a general shift over the course of the show's production. During the beginning of the show's production, the delta had a significantly lower center edge. As the show progressed, however, the combadge's delta tended to bring the lower center edge up further.

An All-Silver variant of the TNG Combadge is worn by Wesley Crusher in TNG while he serves as an acting ensign. This all-silver model still has the black outline for the delta, and is otherwise unchanged.

During the TNG episode "Brothers", Commander Data's Combadge was shown being opened by Dr. Noonian Soong. This was a variant of the normal prop produced just for this scene.

Star Trek: Picard Reproduction
For the production of Star Trek: Picard, property master Jeffery Lombardi produced new versions of the TNG Combadge as well as the VOY Combadge for flashback scenes involving Jean-Luc Picard. In one flashback, he's and Commander Data are wearing their TNG-era uniforms.

This combadge seems to have a much thicker ridge, and uniquely doesn't feature any black outline around the delta. It's believed that these were resin 3D printed, much like the majority of the props made for Star Trek: Picard. It appears to be fairly accurate to the original otherwise, in terms of depth and curve.

Production
TNG Combadges were produced by the Prop Department at Paramount Studios. They were produced by pouring resin into a mold, and then spraypainting them. The paints used are believed to be Krylon Bright Gold 1701 and Krylon Dull Aluminum 1403. The Black Outline was achieved simply using a Black Sharpie. Finally, a square hole was carved out using a Dremil or rotary tool, and then a small piece of 3M Velcro was placed inside the badge. The costumes worn by actors would have a matching square of Velcro for the combadge to rest on. For scenes where combadges had to be taken off, it's believed that magnets or pins were used instead, and a variant of the costumes without a Velcro square were used in these instances.

Modern prop makers have tried variations on which paints to use, and as with most spray paints, no two cans will be alike, especially if there's 30+ years difference between the original production of the paint and now. Some alternatives include: Krylon Chrome Aluminum, and Dupli-Color Instant Gold.

Reproductions
Combadges are some of the most widely re-produced props in the Star Trek fandom, due to their low cost and ease to produce.

In the late 80s, Lincoln Enterprises, a small pin manufacturer run by the Roddenberry family, sold a few variations of the combadge pin. These aren't accurate to the original at all, but were designed using the original combadge as a base, and geometrically have a linage to the original. One example was cast in pewter, and painted with a very similar color to the Krylon Gold color. Another example was a polished Cloisonné silver and gold combadge, which is now commonly duplicated. The easiest way to identify a Lincoln Enterprises badge is to look for the Paramount copyright on the back of the badge. There was also an oversized toy combadge sold by Playmates Toys in the 90s.

Resin Badges (Screen-Accurate Replicas)
Roddenberry.com used to sell combadges, produced by Xscapes Sci-Fi Originals. However, Roddenberry.com closed it's shop and sent the remaining stock to Entertainment Earth, where it is now sold out. Xscapes still carries them through their website, and they are widely regarded as the best replica of the TNG Combadge, as it was reproduced using a re-cast of a screen-used combadge.

Some manufacturers of badges like to use resin 3d printing for production, and many examples can be found on Etsy and eBay. One of these is FamousPropTreasures, an independent builder from the UK. Their badges are extremely clean and sharp, but this does detract from the accuracy to the original combadges. In general, production-made combadges are a bit more "worn" since they were cast from resin and hand-painted. However, FamousPropTreasures seem to be the most color accurate combadge produced in this manor, as of writing.

Metal Badges (QMX)
QMX sells a commercially-available combadge made entirely of metal. These are widely regarded as the best cheap combadge replica, and they are popular among casual cosplayers. They are heavy in weight due to being made of all metal, and are magnetically clasped to the costume, which makes it easy to adhere to surfaces without leaving damage from a pin-back. However, they are bright and shiny, a design decision made by QMX during production. This makes them obvious to not be accurate to the original, and are therefore considered less of a replica and more of a premium product. The QMX combadge is also cloned by companies like Cosermart, so be cautious when buying them as it can be easy to fall for a fake.

QMX did at one point sell a framed set of combadges cast in resin, including the VOY Combadge and Bajoran Combadge. These are much more accurate than the metal combadges, as they were created directly from the master molds for the TNG badge. These are no longer sold and can be highly sought after.

Trivia

 * Generally, after the late-2000s auctions in which CBS sold most of it's Star Trek props and costumes, combadges were mostly sold with their uniforms, with only distressed and unique combadges sold on their own. Nowadays, it's more likely that a combadge will be sold on it's own for almost the price of a costume itself.
 * Combadges were commonly stolen from set due to their size. Due to the lack of evidence regarding stolen material, and the difficulty of screen-matching such a small device, it's very difficult to verify the identity of a combadge. It's best to verify the provenance of a combadge if you're purchasing one under the guise of it being "screen-used," even when purchasing from a trustworthy seller.
 * Rick Berman, producer of the Star Trek Frenchise at the time, swiped Denise Crosby's combadge off of her uniform after her last filmed scene. According to Berman, this was after Skin of Evil, but actually, her last episode was Symbiosis, as it was filmed out of order. Denise Crosby stated that Rick Berman "ceremoniously ripped off my Communicator badge saying 'you won't be needing this anymore.'"