I think that for a watch to be (a) collectible, it needs to hit that sweet spot of having a great story and having some degree of variety. Speedmasters are, again, a good example. There are tons of different versions replica audemars piguet. Even if you stick to vintage 1960s references that were used in space, you could build a fantastic collection.
Number Ozone Friendly Uses Chemical Components Alternatives Notes
R410A HFC Yes Designed for new R22 applications, but can also be used to retrofit R13b1 systems. HFC 125 - 50% HFC 32 -50%   Long term ozone friendly replacement for R502 / R22 Low GWP
R500 CFC No; banned under Montreal protocol Low temperature R12 CFC. CFC 12 -CFC 115 - R401b; R407d  
R502 CFC No; banned under Montreal protocol Widely used low temperature refrigerant in the United Kingdom. HCFC 22 -48% CFC 115 -52%    
R503 CFC No; banned under Montreal protocol Low temperature refrigerant -80 to -100°C.   R95, R508a, R508b  
R507 HFC Yes Low temperature refrigerant - application similar to R502/R404A HFC 125 -50% HFC 143 -50%   Long term ozone friendly replacement for R502 / R22
R508A HFC Yes Low temperature replacement for R503. HFC 23 -39% HFC 116 -61%   Long term ozone friendly replacement
R508B HFC Yes replacement for R503.     Long term ozone friendly replacement
R600a HC Isobutane Hydrocarbon, possible long term alternative for small units. Designated flammable.      
R717 NIK Ammonia Refrigerant in large industrial systems. Toxic and Flammable      
R1150 HC Ethane Ultra Low Temperature Refrigerant. Designated Flammable      
R-1270 HC Propylene Low Temperature Refrigerant. Designated Flammable      
HC-30 Hydrocarbon blend Hydrocarbon blend R600a/R290 for R12 application      
HC-50 Hydrocarbon blend Hydrocarbon blend R290/R1170 for R502 applications      
R413 HFC Yes Drop-in for R12 applications, high global warming potential R134a
Perfluorobutane propane
 R401a R408a R409a Ozone friendly but high GWP
R290 HC Propane Designated flammable.      
R401A HCFC No; Will be banned under Montreal protocol High temperature R12 applications. Evaporating at-15°C and above. HCFC 22 -53% HCFC 124 -34% HFC 152a -13%   Short term non ozone friendly blend
R401B HCFC No; Will be banned under Montreal protocol R12 Low temperature alternative. Evaporating at -15°C and below. HCFC 22 -61% HCFC 124 -28% HFC 152a -11%   Short term non ozone friendly blend
R401C HCFC No; Will be banned under Montreal protocol Specialist application R12 alternative. HCFC 22 -33% HCFC 124 -52% HFC 152a -15%   Short term non ozone friendly blend
R402A HCFC No; Will be banned under Montreal protocol Low temperature R502 alternative HCFC 22 -38% HFC 125 -60% HC 290 - 2%   Short term non ozone friendly blend
R402B HCFC No; Will be banned under Montreal protocol High performance R502 alternative HCFC 22 -60% HFC 125 -38% HC 290 - 2%   Short term non ozone friendly blend
R403A HCFC No; Will be banned under Montreal protocol High performance R502 alternative HCFC 22 -75% HC 290 - 5% FC 218 -20%   Short term non ozone friendly blend
R403B HCFC No; Will be banned under Montreal protocol Alternative to R502. HCFC 22 -56% HC 290 - 5% FC 218 -39% R401a R409a Short term non ozone friendly blend; high GWP
R404A HFC Yes Widely accepted HFC alternative to R502 for new low temperature applications. HFC 125 - 44% HFC 134a - 4% HFC 143a -52%   Long term ozone friendly replacement for R502 / R22
R407A HFC Yes Alternative to R404A; low GWP HFC 32 -20% HFC 125 -40% HFC 134a- 40% R404a Long term ozone friendly replacement for R502 / R22 Low GWP
R407B HFC Yes Retrofit alternative to R502 HFC 32 -10% HFC 125 -70% HFC 134a- 20%   Long term ozone friendly replacement for R502 / R22 Low GWP
R407C HFC Yes R22 alternative for direct expansion systems operating at high temperatures. HFC 32 -23% HFC 125 -25% HFC 134a - 52%   Retro fitable - Long term ozone friendly replacement for R502 / R22 Low GWP
R407D HFC Yes HFC Retrofit alternative for R500 HFC 32 -15% HFC 125 -15% HFC 134a -70%   Long term ozone friendly replacement for R502 / R22 Low GWP
R407E HFC Yes HFC retrofit alternative to R22 R134a; R125; R32   Long term ozone friendly replacement for R502 / R22 Low GWP
R408A HCFC No; Will be banned under Montreal protocol R502 alternative for medium and low temperatures HCFC 22 -47% HFC 125 - 7% HFC 143 - 46%   Short term non ozone friendly blend
R409A HCFC No; Will be banned under Montreal protocol R12 high temperature alternative. HCFC 22 - 60% HCFC 142b-15% HCFC 124 -25%   Short term non ozone friendly blend
R409B HCFC No; Will be banned under Montreal protocol low temperature R12 alternative HCFC 22 -HCFC 142b -HCFC 124 -   Short term non ozone friendly blend
CFC No; banned by Montreal Protocol Foam blowing agent, refrigerant, aerosol solvent: flushing systems Should NOT be used with R134a Trichlorofluorornethane R123 Short term HCFC and not easily retrofitted
fl-12 CFC No; banned by Montreal Protocol Used for high/low temperature refrigeration applications, domestic refrigerators, foam blowing agent, aerosol propellant Dichlorodifluoromethane R134a R401a/b/c/ R409a R406 Requires ester oil for retrofit Drop in's but may need Alkyl Benzene oils to be sure, Short term replacements
R-13b1 CFC No; banned by Montreal Protocol Low temperature refrigerant-40 to -60°C.   R410a  
fl-13 CFC No; banned by Montreal Protocol Low temperature refrigerant Chlorotrifluoromethane R23 Not easily retrofitable
R-22 HCFC No; Will be banned under Montreal protocol Low, medium, and high temperature refrigeration and air conditioning, also foam blowing. And aerosol propellant Chlorodifluorometane R407C R404a R410a Retrofitabie R410a much higher pressure
R-23 HFC Yes Low temperature refrigeration systems: -40 to -80 °C. Trifluormethane    
R-32 HFC Yes Low temperature refrigerant, designated flammable. Difluoromsthane   Used on R407 series of refrigerants, low GWP
R113 CFC No; banned by Montreal Protocol Limited application in Centrifugal refrigeration systems, widely used as a solvent in the dry cleaning industry. Trichtorotrifluoromethane R123 Retrofit is not easy. Short term affected by protocol.
R114 CFC No; banned by Montreal Protocol Widely used in heat pump applications. Tetrachloromethane R124 - retrofit R124 not easily retrofitted
R115 CFC No; banned by Montreal Protocol Principally used as a component for R502 Pentafluorochloroethane R125 in blends  
R116 HFC Yes Used as a component in R95, with no other known refrigeration applications. Hexafluoroelhane    
R123 HCFC No; Will be banned under Montreal protocol Used as a retrofit alternative to R11/R113 (See notes on these products) Dichlorotrifluoroetane   Short term R11 replacement
R124 HCFC No; Will be banned under Montreal protocol Can be used as an alternative to R114 in heat pump applications (see notes on R114) Chlorotetrafluoroethane   Short term replacement for R114; mainly used in short term blends to replace
R125 HFC Yes Used as an alternative to R115 and a component in blends 404a, 507, 408a Pentafluoroethane   Long term replacement for use in blends
R134a HFC Yes Used for high/medium applications. Foam blowing agent, a component in blends. 1,1,1, tetrafluoroethane   Long term replacement for R12 in medium to high temp uses, requires est oils
R141B HCFC No; Will be banned under Montreal protocol Widely used as a foam blowing agent. Trichlorofluoroethane Cyclopentane or H/C's Short term replacement soon to be replaced
R142B HCFC No; Will be banned under Montreal protocol Used as a component in blends. Chlorodifluoroethane   Short term use in non ozone friendly blends
R143a HFC Yes Used as a component in blends, cf. R125 Designated flammable. Trifluoroethane   Long term use in ozone friendly blends. High GWP
R152a HFC Yes Used in blends, also in the glass industry for floating various lustre's. Designated flammable. Difloroethane   Not commonly used as refrigerant
R218 HFC Perfluoro-propane Component in some blends.     High global warming potential
CFCs: Chlorofluorocarbons. These products have ceased production within the RSA for internal consumption with effect from 1996.
HCFCs: Hydrochlorofluorocarbons. Full availability within the RSA, and the present production phase out date is 2015. There is a widespread belief that this will be reduced to 2005 within the next 2-3 years.
HFCs: Hydrofluorocarbons. At the moment there is no production phase out date for HFCs and there is unrestricted use on their applications.
HCs & NH3: This product group mainly used in industrial equipment due to flammability concerns.