For the purposes of making this easy, I'm using TFU.info as a reference, purely because it allows searching by year, which the Seibertron database to my knowledge, currently doesn't easily allow for beyond G1.
STEP 1:
The first thing to point out for anyone reading this is don't panic. While there have been over a thousand Transformers produced in the line's 30 year run, tracking down that elusive mystery figure is surprisingly and relatively easy.
The first thing you need to do is look for a date stamp on the figure. Generally you'll be able to see it on close inspection of a figure, if you check every visible surface of the toy for it.
In this case, let's go with Perceptor from 1986 with a photo of his back:
The date stamps will vary in how they show the year. Some date stamps will display the full year, whilst others, on smaller figures will display the year in 2 digit format - for example, 2005 will be displayed as '05.
Once you have that, you know the year the mold for the figure was originally made. As a general rule of thumb, molds tend to be created a year before a toy shows up at retail.
However there are a few exceptions to this. In more recent year, some figures will have molds produced at the very beginning of that year and the figure will show up at the very end of the year at retail.
The other exception to this is with the very early Transformers from 1984-1986. Most of these toys were taken from other toylines and so you will find 2 years listed on their date stamps on them. In some cases, take the latest year as the one you need to look for. Also with the very early Transformers, some figures from 1986 will have a date stamp on them which says "1984".
As a general rule of thumb though, you should take the date stamp as an indication that a figure was released that year or the following year.
STEP 2:
Before I go on here, it's important to explain the meaning of 2 particular terms you'll encounter - recolours and retools. Recolours of course, is mostly self explanatory. With a recolour, the toy itself is physically identical to another toy, but is a completely different colour scheme.
An example of this is this photo of Starscream with Skywarp to his right and Thundercracker to his left:
The other term to discuss here is a remold or retool. With remolds or retools, in addition to a possible different colour scheme parts have either been changed or added to a figure, meaning that the tooling or molding on a figure has been changed, hence the term "remold"/"retool".
Three figures which are great examples of this are [left to right] Smokescreen, Prowl and Bluestreak:
As you can see, whilst Bluestreak [right] is the original mold/tooling, Prowl [centre] has had a police siren added, whilst Smokescreen [left] has had the front end of the car altered and a spoiler added to the rear of the car.
That said; having identified the date stamp, go to the search by year option on TFU, and select the appropriate year.
While you may get lucky and find exactly what you're looking for, the goal at this point is to find a figure which looks almost identical to the one you are looking for.
If you find a figure that looks almost identical but is a different colour or has different parts, scroll down to the bottom of a figure's entry. There you will find a list of recolours and retools of the figure, allowing you to identify the mystery figure.
Congratulations, you now know what figure which you or your child are the proud owner of.
STEP 4: [OPTIONAL]
Ok so now you know what figure you have, but maybe you're not sure exactly how to transform it. Why couldn't the seller you got it from have kept the instructions? Whatever will you do?
Fear not, because in 99% of cases, it's really straightforward to download instructions for the toy in question. For everything upto and including the Transformers Armada line from 2002-2003, Fort Max's Transformers Instruction Archive will be your go to place for the instructions you need.
However failing that, Hasbro have an online database of instructions to download. however it is slightly problematic.
While in many cases finding the instructions you need are straightforward, in some cases, Hasbro only have instructions for one particular colouring or tooling of a particular mold. In those cases, you may have to search for a different colouring or tooling of the same mold. However in 99% of those cases where Fort Max's Archive doesn't have what you need, Hasbro's online database will have what you need.
