A brief Primer on ReMarriages
200 years ago coin dies were expensive and hard to make. Back then when a die became damaged it would be pulled, repaired and placed back in service. Remember too that at times obverse dies with dates may have been used after the date on the coin. No sense throwing away a perfectly good obverse die just because it has the wrong date on it!
Using reverse E as an example we'll show how this worked.
Reverse E was first used in 1829 paired with the obverse 4 die which created the 1829 LM6.1. At some point the obverse 4 die was pulled and replaced with an obverse 5 die (creating the LM7 variety) and mintage continued. At some point the obverse 5 die was pulled and replaced by the obverse 4 die used earlier creating the LM6.2. By this point the E reverse die was showing some degradation with the first diagonal of the N filling with a die chip. Also seen is a small cud above M and a die crack forms from the rim through the top of E 3. For the purposes here, discussions on remarriages are brief. For more in depth discussion on remarriages please see the Logan  McCloskey book, "Federal Half Dimes 17921837".
Using reverse E as an example we'll show how this worked.
Reverse E was first used in 1829 paired with the obverse 4 die which created the 1829 LM6.1. At some point the obverse 4 die was pulled and replaced with an obverse 5 die (creating the LM7 variety) and mintage continued. At some point the obverse 5 die was pulled and replaced by the obverse 4 die used earlier creating the LM6.2. By this point the E reverse die was showing some degradation with the first diagonal of the N filling with a die chip. Also seen is a small cud above M and a die crack forms from the rim through the top of E 3. For the purposes here, discussions on remarriages are brief. For more in depth discussion on remarriages please see the Logan  McCloskey book, "Federal Half Dimes 17921837".


Listed to the left are the rarest 25 die marriages both by date and by R factor.
Rarity Rating R4 = 76 to 200 Pieces Known R5 = 31 to 75 Pieces Known R6 = 13 to 30 Pieces Known R7 = 4 to 12 Pieces Known R8 = 1 to 3 Pieces Known The "Holy Grail" in the series is the 1835 LM12 of which just 3 to 4 pieces exist followed closely by the 1830 LM1.1 with 3 known pieces and the 1833 LM5 with only 5 known examples. 
1829 LM6.1 R7, LM6.2 R5, LM6.3 R5
The 1829 LM6 varieties combines obverse 4 with reverse E
Identifing the 1829 LM6 Varieties  6.1  6.2  6.3 

Strong devices, both berries have stems  yes  yes  yes 
First diagonal of N fills  No  yes  yes 
Small cud starts to form above M into dentils  No  yes  yes 
Top loop of S2 fills. Die crack forms from  
left wing tip to rim  No  No  yes 
Large die chip forms in second angle of N and a  
die crack forms from rim to top of E3 & across to R  No  No  yes 
1829 LM8 R6
The 1829 LM8 R6 combines obverse 2 with reverse E
1829 LM11 R6
The 1829 R6 LM8 combines obverse 2 with reverse F
1829 LM12 R6
The 1829 R6 LM12 combines Obverse 5 with Reverse F
1830 LM1.1 R8
The 1830 LM1.1 R8 combines obverse 1 with reverse G
Identifying the 1830 LM1 Varieties  LM1  LM2 

Die crack forms from tip of right wing to  
arrow shafts  No  Yes 
Die crack forms from the base of A2 to F  No  Yes 
Cuds form at top of A2 and through tops  
of ERI  No  Yes 
1830 LM5 R6
The 1830 LM5 R5 combines obverse 1 with reverse J
1830 LM9.2 R5
The 1830 LM9.2 R5 combines obverse 5 with reverse L.
Differentiations between the LM9.1 and LM9.2
Differentiations between the LM9.1 and LM9.2
9.1  9.2  

Top loop of S1 & S2 Filled  No  Yes 
Top right of T1 filled  No  Yes 
M fills between right upright and Diagonal  No  yes 
Die crack appears at tops of UNIT  No  Yes 
Die crack appears from Scroll end to top of  No  Yes 
right wing over to E3  
Die crack begins to form from left wing tip  No  Yes 
to olive branches then to rim 
1830 LM10 R6
The 1830 LM10 R6 combines obverse 5 with reverse F
1830 LM11 R6
The 1830 R6 LM11 combines obverse 4 with reverse M
1832 LM8.2 & LM8.3 R5
Identifing the 1832 LM8 Varieties  8.1  8.2  8.3  8.4  8.5 

1st use of T reverse, strong rim and dentils  Yes  No  No  No  No 
5th use of T Die swelling hides BU in PLURIBUS  No  Yes  No  No  No 
Top loop of S2 starts to fill  No  Yes  
Top loop of S2 filled  No  No  Yes  Yes  Yes 
Die crack appears from E1 through scroll,  
through eagle's head to scroll below N  No  Yes  Yes  Yes  Yes 
Top loop of S1 filled  No  No  Yes  Yes  Yes 
Die chip forms between right upright and  
diagonal of N  No  No  Yes  Yes  Yes 
Die cracks appear at base of UNIT ES MERIC  No  No  No  Yes  Yes 
More die cracks appear from rim to M, F to rim  
and from right wingtip passing through  
arrows to rim  No  No  No  Yes  Yes 
Die crack at bottom of IT enlarges and joins IT  No  No  No  No  Yes 
N fills between right upright and diagonal  No  No  No  No  Yes 
Die chip forms in D  No  No  No  No  Yes 
The 1832 LM8.2 & 8.3 R5 combines obverse 4 with reverse T
1832 LM9.1 R6 & LM9.2 R7
Identifing the 1832 LM9 Varieties  9.1  9.2 

Top Loop of S2 Filled  No  Yes 
The 1832 LM9.1 R6 and LM9.2 R7 combines obverse 2 with reverse T
1832 LM10.2 R6 & LM10.3 R5
Identifing the 1832 LM10 Varieties  10.1  10.2  10.3  10.4 

Die chip between right upright and diagonal of N  No  Yes  Yes  Yes 
Die crack from left wingtip to dentils  No  No  Yes  Yes 
Die crack from from top of A2 to M in scroll  No  No  Yes  Yes 
Monster cud developes over TES OF A  No  No  No  Yes 
The 1832 LM10.2 R6 and LM10.3 R5 combines obverse 4 with reverse U
1832 LM11.1 R5
Identifing the 1832 LM11 Varieties  11.1  11.2 

Die crack from left wingtip to dentils  No  Yes 
The 1832 LM11 R5 combines obverse 2 with reverse U
1833 LM2 R6
The 1833 LM2 combines obverse 1 with reverse T
1833 LM3.5 R7
The 1833 LM2 combines obverse 2 with reverse T
Identifing the 1833 LM3 Varieties  3.1  3.2  3.3  3.4  3.5 

Upper loop of S2 filled  No  Yes  Yes  Yes  Yes 
Die chip begins to form between upright and  
center bar of E1  No  No  Yes  Yes  Yes 
Die cracks form between right wing tip through  
arrows to rim and from rim to top of A3  No  No  No  Yes  Yes 
Large cud covers NIT and portion of E  No  No  No  No  Yes 
1833 LM4.3 R5
The 1833 LM4.3 combines obverse 2 with reverse U
Identifing the 1833 LM4 Varieties  4.1  4.2  4.3 

Die chip forms between diagonal and right  
upright of N  Yes  Yes  Yes 
die crack forms from left wing tip to dentils  No  Yes  Yes 
Cud forms top of scroll to F A  No  No  Yes 
1833 LM5 R7
The 1833 LM5 combines obverse 2 with reverse P
1833 LM6 R6
The 1833 LM1 combines obverse 1 with reverse W
1835 LM12 R8
The 1835 LM12 combines obverse 4 with reverse JJ
1837 LM3 R5
The 1837 LM3 combines obverse 3 with reverse LL