Yes, however the swingweight may change dramatically so the club may not feel correct (too heavy or light). Thus, it may be time to upgrade the set....however the new sets are much more forgiving so you may actually play even better as a result!

Once I needed an additional club to match my set and wrote to the manufacturer with the serial number and they sent me the additional club to match my set, at the current value price. I realize you have already purchased that iron off eBay, but you might check with a Titleist retailer or a pro shop and see if you can get a replacement club if you really like those 712s. I agree with Chris, the technology on the new clubs is off the charts.