Converting an Antique Pin

I’ve now converted an antique stick or bar pin into a wearable piece of jewelry several times, and I’ve learned some lessons in case you want to try the same.  Here are the 10 most important ones.
1.      Look carefully at the condition the item is in before you decide to buy.  There should not be any “dings” or other imperfections. It’s very hard to remove or change those.
2.      Make sure you know how much the pin weighs. Figure that half of it, if it’s a stick pin, is the stick itself.  But: sometimes the stick itself is not gold.  It happens that the old pin back has broken off and a new one, silver or even lead, has been soldered on.  This not always easy to tell.  So if you are assuming you can sell the back and get part of your money back, make sure it’s gold.  If you can’t test it at home, look for a stamp.  I’ve had it happen several times that the antique dealer, eBay seller, or Pawn Shop, only tested the front of the stick pin, and not the stick itself (so it might not hurt to ask).  On average, if you can scrap the stick, you will get between $10 and $20.
3.      Assume that if the pin contains a colored stone, the stone is fake.  Many, if not most, of the gems used in that antique jewelry from about 1900-1930 are not real.  So what you pay should not include the stone.  If you do get a pin with a colored stone that was advertised as real, you need to have it tested.  And be aware that not all jewelers are good at this.  I take mine to the lab because even some “jeweler’s tested” stick pins that I bought have contained fake colored stones.  I didn’t complain though because I didn’t bet on the stone, and I know how hard it is to tell.
4.      If you want to replace the center stone, make sure there’s enough prong left to hold the new gem, and choose a flat stone if the original was a diamond, because they are cut more shallow than most colored stones.  Replacing the center stone without the help of a jeweler that can rebuild the prongs, or a good setter, is not really an option for you.
5.      If the center gem is a diamond (and advertised as tested), you can assume it is real.  The easy test is to scratch it with a sharp instrument to double check, but jewelers are usually good at testing diamonds.  I therefore recommend only diamond stick pins.  So far every diamond stick pin I have bought has had a real diamond.
Two pins before conversion
6.      The diamond should be an old miner.  How will you know?  Old miners have a deeper cut, an open culet and different facets (you can find pictures online).  Some old miners are single cut (they have fewer facets) and those have less value.  Some signs of wear are also common.  That means that the facets are less defined. This is ok.  Don’t try to have it fixed.
7.      When you convert your pin into a pendant, you need a bail and a jump ring.  It is best if you buy the parts yourself, that way you don’t get overcharged. 
8.      Converting is best done via lazer solder, not regular solder.  Regular soldering is too hot, and any colored stone will not survive.  Diamonds can take more heat, so those are ok to solder the regular way.
9.      Most antique dealers do not clean old gold, because some customers don’t like it.  I do have it cleaned because it does get a whole lot prettier that way, but I do not get white gold rhodium plated to keep the old fashioned look.  Just a light polish is best.
10.   If you want to have your piece cast, it cannot have too much detail.  Most casting services require 1/3mm depth for a mold to “pick up” any pattern, including an engraving.  Also, the silicone has to get behind and in between all the filigree, and that rules out a lot of pieces. 
After conversion (I added an element)