is there a difference of flemmings sear like fleammin H and just a flemming. can a Flemming H be put into h_&_k mp models such as the 5 the s_d or the k

What you are asking about are the Fleming Firearm Heckler & Koch conversion sears where the prefix of the Serial # on the sear begins with an "H" and is usually followed by 3 or 4 digits.  

These sears are machineguns unto themselves and can be installed into any properly prepped S-E-F or "Ambi" (Navy or Burst) trigger pack.   These trigger packs once properly set up with a Fleming conversion sear can be installed on any 9X style HK variant  (MP5, MP5SD, K, 53,33, 51, G3, 21, etc.)    The "H" series of sears are identical to the Qualified Mfg "K" series of sears as they were made at roughly the same time on the same dies.   Both the Fleming H and Qualified K sears were made from heavy gauge stamped steel and should last a lifetime.

My understanding is that Fleming did make some early sears out of milled bar stock but that these sears were used in married conversions and that they would not be machineguns unto themselves.   In 15 years of collecting MGs and HK I have never seen a stand-a-lone barstock milled Fleming sear for sale.  I am not saying they dont exist, as they may very well be out there.  However, the vast majority of the sears are going to be the stamped "H" series variants.   That said a milled barstock sear should function identically in a SEF or Ambi pack and be able to convert any Semi Auto 9X series rollerlocked sheetmetal HK into a machinegun.

The Stamped steel H Series would in my estimation always command a premium as they are a known quantity vs any other Fleming sear.

JBinTex is correct, but I have seen 2 Fleming firearms milled HK auto sears with serial numbers on them.  Both were badly worn, since the ledge that engages the full auto hammer was hitting the full auto hammer where it has a relief cut.  Both sears had to be welded on, milled and reheat treated.  The hammers had to be recut, merely a new flat had to be ground to allow the auto sear to clear the falling hammer.

The MG smith who did the work advised that the first Fleming sears all had that problem, and as JBinTex advised, Fleming put all the remaining bar stock auto sears in the MP5's and G3 conversions he did for Fred Vollmer just after the 86 ban.  If you bought a registered receiver Mp5 or G3 conversion from Vollmers with the push pin receivers, flapper mag releases and bondo covered H&K markings with new stamped MP5 or G3 markings, those were the ones that had these in them.  One Class 3/2 upgraded all the Fleming/Vollmer registered receivers that went through his shop in PA, and he had a glass jar filled with these milled sears.  He just put in factory auto sears and hammers in the packs, and those that had the converted HK90 semi packs, he just put in factory full auto SEF trigger frames and packs in their place.  I know he dumped all the spare converted 90 semi pack/trigger frames and hammer on the old Vollmer Board, but the Class 2 and Vollmer are both out of business now so no more links to the pics they used to have.

This does not apply to the Qualified Manufacturing sears done by Arville Sellmeyer, as I dont recall if he used the leftover Qualified Sears for his business or if he had any from his H&K work before the 86 ban.