Pre War Conversion kit
 

I have a Luger conversion kit, in a high grade, oak wood box, with metric measurements. Each part is proofed with an eagle over the number 280. The spine of the magazine is marked with an eagle over the number 77. The left side of the magazine is similarly marked. The serial number is 43XXa. The barrel and toggle bear the same serial number as does the metal plaque embedded in the inside of the bottom half of the box. All parts are blued. The barrel is 7 inches plus. The top of the toggle, rear half, also bears a double EE in a circle.

There is no manufacturer marking.

Can't post pictures as I don't know how. If you send me your e-mail, I will send pictures.

Any help would be appreciated.

Many thanks.

The EE is the makers mark, for Erma; earlier units were marked Erma over Erfurt in two styles.

Posting pictures is not difficult; check the sticky's for how; or email me the pictures and I'll post.
Email to donvoigt at hotmail.com

Yours sounds like the "usual" luger sub caliber kit and box; the markings are the usual ones.
These came in to size boxes, a large about 14" long and a short one about 8" long. The small box shown below is a reproduction, the long one likely original. The boxes were often marked also.

Here are the OP's pictures he sent me.

Reproduction box, basic kit pieces.