Unusual Lee Enfield Magazine

I recently brought home a long Lee Speed/Enfield LSA commercial rifle. On closer inspection I found that the magazine doesn't look quite right. It does not have the chain ring normally found on Long Lee magazines, the rifle still has the chain link. The magazine does not resemble a modified MK3 or No.4 magazine. I cannot find a reproduction magazine that has the same shape. The magazine resembles a Metford magazine but holds 10 rounds.
The magazine is assembled in a similar way to a regular factory Enfield magazine. It appears to be as old as and in the same condition as the rifle. Pictures soon.

---------- Post added at 06:39 PM ---------- Previous post was at 06:34 PM ----------

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Looks like a commercial pattern magazine. Which makes sense, since you got it with a commercial rifle. Very nice and high quality. I too have a commercial rifle (BSA) and it's magazine is almost identical to yours. The only exception is it has a standard enfield follower.

Heres my Long Lee w/mag.

Commercial BSA MLE Mk I with no mag chain or loop. Non-safety bolt with 5-groove enfield rifling. Squared mag body and solid back-rib. Similiar to yours, but has a different follower.