looks like this question came up before ..and a chuggerpumps rep answered it with this statement,
"All that is up for debate among brewers...I strongly believe that any food processed fluids( especially when they are heated) should be in contact with FDA food grade materials only. Ceramic Ferrite magnets are not FDA. These all come form China. All the Chugger and March magnets are encapsulated in Stainless just for this purpose. How much did you pay for this pump with Shipping ?"
and
"There is no such thing as a food safe magnet! We are dealing with Ferrite metals here..definitely not food safe. No HI- Jack intending here ..I just cant stand it when false statements are made about food safe materials . On all other brands of brew pumps the magnets are encased in either SS or Polysulfone FDA grade plastic ....this is for a reason! Dont be mislead
My 2 cents ..maybe we both should be deleted? Joe ...call me would love to discuss further
MIKE 800-810-1053"
and yet another quote from him
"High temp food grade coating?? We have been selling FDA grade pumps for 20 years...never heard of it? Please forward what this is ..we could spray all of aour cast iron pumps with it and make them food grade?
The point here is it does not exist!"
https://www.homebrewtalk.com/f11/looking-pump-input-317600/index13.html
it appears that 3 years ago SOME of the topflo pumps being sold had started being modified and had the magnets coated with a visable coating some of the older pumps had a less robust clear silicone based coating... according to what I'm still reading the stainless threaded ones had the better coating but not the brass of plastic...
according to chugger pumps testing the topsflo only had 2gpm flow with little head pressure... thats actually the same as I measure with my tan 24v pump with my rotometer pumping from the bottom of my kettle thru my rims and up into the top of another...
Here is another quote from a big reseller "beerpumpsect" (GreatbrewEH) from 3 years ago
"I can tell you the product is silicone which we all use in the tubing (FOOD GRADE) including us. I cannot tell you the specific product as we have worked hard to modify this pump for this purpose and continue to do so like any other decent company. The newest coating is going to be more apparent in attempt to end the doubt. I am certain the certification will meet all expectations.
Please be assured these are not the same pumps others refer to from ebay, they are the same basic motor and ryton head but that's it, they were designed for another purpose all together.
Finally one day in the future, (please do not email when) we are working on an all stainless steel head so once again we can totally put this to bed. There are many brewing days ahead so don't wait.
PS. I have loved mine and continue to happily use them but those who wish to pay more for other brands because they feel it is a better choice for themselves, I completely support you in that decision and wish you happy brewing with whatever equipment gets you to the finish line.
GBE"
so it looks like the the all stainless head TD4 has been at least 3 years in the making and the first shipment went out on 06-12-2012, (sorry wbarber69 but they didnt design it for you) and unless you have a "noticable coating" on the magnet you have one of the questionable pumps not modified for berr pump use...