One matched pair Mullard CV3998 (6688) gold pin tubes, by Philips of Heerlen plant.

One tube also labelled Sylvania.

There are no insert marks on the pins, and at NOS ratings, the tubes look new to me.

Philips Heerlen codes: delta4I8 and delta5B4.

Test Ratings:  105 to 110  in my Jackson 648s tester, minimum is 70, new tubes at about 105 to 110.

SHIPPING: Shipping to USA and Canada only with tracking. For Europe and Far East countries, please contact the Seller to get permission to buy ( due to higher tracking fees charged by Canada Post).

Please pay in 3 days. Combined shipping is welcome. If you have paid for individual items and have surplus shipping fee paid for, I will refund you immediately when I send out the combined parcel.